Electrophotographic photoreceptor and image forming apparatus including the same

ABSTRACT

An electrophotographic photoreceptor of high durability capable of providing stable excellent electrical characteristics over a prolonged period of time, which electrophotographic photoreceptor excels in mechanical strength. A photosensitive layer ( 14 ) of an electrophotographic photoreceptor ( 1 ) includes a polyarylate resin having structural units, for example, those of formula (1) 
                         
and an enamine compound represented by, for example, formula (2)
 
                         
The variables R 1 , R 2 , R 3 , R 4 , R 7 ˜R 10 , X 1 , Ar 1 , Ar 2 , Ar 3 , Ar 4 , Ar 5 , R 11 , R 12 , R 13 , R 14 , a, m, and n are as defined in the specification. By virtue of these, the electrophotographic photoreceptor ( 1 ) of excellent mechanical strength and favorable electrical characteristics can be realized.

TECHNICAL FIELD

The present invention concerns an electrophotographic photoreceptor, aprocess cartridge having the electrophotographic photoreceptor, and anelectrophotographic apparatus and, more specifically, it relates to anelectrophotographic photoreceptor having a photosensitive layercontaining a specified resin and a specified charge transportationsubstance, a process cartridge having the electrophotographicphotoreceptor, and an electrophotographic apparatus.

The present invention concerns an electrophotographic photoreceptor usedfor electrophotographic image forming apparatus such as copyingmachines, printers and facsimile apparatus, and an image formingapparatus having the same and, more specifically, it relates to anelectrophotographic photoreceptor having a photosensitive layercontaining a specified charge transportation substance and a specifiedresin, and an image forming apparatus having the same.

The invention concerns an image forming method and an image formingapparatus for forming images by an electrophotographic process and, morespecifically, it relates to an image forming method and an image formingapparatus for contacting a charging member with an electrophotographicphotoreceptor and conducting charging.

BACKGROUND ART

In recent years, the electrophotographic technique has been utilized notonly to the field of copying machines but also to the fields of printingmaterials, slide films or microfilms for which the photographictechnique was used so far, and it is applied also to high speed printersusing lasers, light emitting diodes (referred to simply as LED), orcathode ray tubes (referred to simply as CRT). In theelectrophotographic process in which images are formed using theelectrophotographic technique, image formation is carried out asdescribed below. At first, the surface of an electrophotographicphotoreceptor (hereinafter also referred to simply as ‘photoreceptor’)is charged to a predetermined potential and exposure is applied inaccordance with image information to the charged surface of thephotoreceptor thereby forming electrostatic latent images. The thusformed electrostatic latent images are developed with a developercontaining a toner and the like and visualized as toner images. Imagesare formed by transferring the toner images from the surface of thephotoreceptor to a recording medium such as paper and fixing thetransferred images. Along with development for the application range ofthe electrophotographic technique, demands for the electrophotographicphotoreceptor have become severe and versatile more and more.

An electrophotographic photoreceptor comprises a conductive supportformed of a conductive material and a photosensitive layer on theconductive support. As the electrophotographic photosensitive material,inorganic photoconductors having photosensitive layers comprising, asthe main ingredient, inorganic photoconductive materials such asselenium, zinc oxide or cadmium have been used generally. While theinorganic photoreceptors have a basic characteristic as thephotoreceptor to some extent, they involve a problem that the filmformation of the photosensitive layer is difficult, the plasticity ispoor and the manufacturing cost is expensive. Further, the inorganicphotoconductive materials are generally highly toxic and impose largerestriction in view of manufacture and handling.

More specifically, typical electrophotographic photoreceptors usinginorganic type photoconductive material (hereinafter referred to as“inorganic photoreceptor”) include, for example, a seleniumphotoreceptor using amorphous selenium (a-Se) or amorphous seleniumarsenide (a-AsSe), a zinc oxide photoreceptor in which zinc oxide (ZnO)is dispersed together with a dye as a sensitizer in a binder resin, acadmium sulfide photoreceptor in which cadmium sulfide (CdS) isdispersed in a binder resin, and an amorphous silicon photoreceptorusing amorphous silicon (a-Si) (hereinafter referred to as “a-Siphotoreceptor”). However, the inorganic photoreceptor involves thefollowing drawbacks. The selenium photoreceptor and the cadmium sulfidephotoreceptor involve a problem in view of heat resistance and storestability. Further, since selenium and cadmium are toxic to human bodiesor environments, the photoreceptors using them have to be recovered anddiscarded properly after use. Further, the zinc oxide photoreceptor hasa drawback of low sensitivity and low durability and it is scarcely usedat present. Further, while the a-Si photoreceptor that attractsattention as an in organic photoreceptor causing no public pollution hasadvantages such as high sensitivity and high durability, it involves adrawback that it is difficult to form a photosensitive layer into auniform film and tends to cause image defects since it is manufacturedby using a plasma chemical vapor deposition (simply referred to as CVD).Further, it has also a drawback that the productivity is low and theproduction cost is high.

Further, development has been proceeded in recent years for thephotoconductive material used for the electrophotographic photoreceptorand organic photoconductive materials, that is, organic photoconductors(simply referred to as OPC) have been often used instead of theinorganic photoconductive materials used so far.

The organic photoconductive materials have been studied and developedgenerally and they are not only utilized for the electrophotographicphotoreceptor but also have been started to be applied, for example, toelectrostatic recording devices, sensor materials or organic electroluminescent (simply referred to as EL) devices.

Since the organic photoreceptor having a photosensitive layer using theorganic photoconductive material (hereinafter also referred to sometimesas “organic photoreceptor”) has advantages that the film formingproperty of the photosensitive layer is favorable, it is also excellentin flexibility, reduced in weight, and excellent in transparency, andcan be easily used for the design of a photoreceptor showing favorablesensitivity to a wide range of wavelength regions by an appropriatesensitizing method, it has been developed gradually as a main stream ofthe electrophotographic photoreceptor. While the organic photoreceptorinvolves some problems in view of sensitivity, durability, and stabilityto the environment, it has many advantages compared with the inorganicphotoreceptor with respect to toxicity, production cost, degree offreedom for the design of material, etc. Further, it has also anadvantage that the photosensitive layer can be formed by an easy andinexpensive method as typically represented by a dip coating method. Inview of the advantages described above, the organic photoreceptor hasgradually become predominant in the electrophotographic photoreceptor.Studies have been conducted particularly in recent years, andimprovement for sensitivity and durability has been intended and theorganic photoreceptor has been used at present as an electrophotographicphotoreceptor excepting for special cases.

Particularly, the performance of the organic photoreceptor has beenimproved remarkably by the development of a function separated typephotoreceptor in which the charge generating function and the chargetransportation function are shared respectively on separate materials.Further, since the function separated type photoreceptor has aphotosensitive layer in which a charge generation layer containing acharge generation substance for charge generating function and a chargetransportation layer containing a charge transportation substance forcharge transportation function are stacked, it has also an advantagethat the range for selecting the materials for the charge generationmaterial and the charge transportation substance is wide, and that anelectrophotographic photoreceptor having arbitrary optionalcharacteristics can be manufactured relatively easily. The chargegeneration layer and the charge transportation layer are usually formedwith the charge generation substance and the charge transportationsubstance being dispersed in a binder resin as a binder.

For the organic photoconductive material used for the charge generationsubstance of the function separated type photoreceptor, varioussubstances such as phthalocyanine pigment, squarylium dye, azo pigment,perylene pigment, polynuclear quinone pigment, cyanine dye, squaric aciddye, and pyrylium salt dye have been studied and various substances ofexcellent light fastness and having high charge generating ability havebeen proposed.

On the other hand, as the organic photoconductive material used for thecharge transportation substance, various compounds such as pyrazolinecompounds (for example, refer to Japanese Examined Patent PublicationJP-B2 52-4188 (1977)), hydrazone compounds (for example, refer toJapanese Unexamined Patent Publication JP-A 54-150128 (1979), JapaneseExamined Patent Publication JP-B2 55-42380 (1980), Japanese UnexaminedPatent Publication JP-A 55-52063 (1980)), triphenylamine compounds (forexample, refer to Japanese Examined Patent Publication JP-B2 58-32372(1983) and Japanese Unexamined Patent Publication JP-A 2-190862 (1990)),and stilbene compounds (for example, refer to Japanese Unexamined PatentPublications JP-A 54-151955 (1979) and JP-A 58-198043 (1983)). Recently,pyrene derivatives, naphthalene derivatives and terphenyl derivativeshaving a condensed polynuclear hydrocarbon system at the center nuclei(for example, refer to Japanese Unexamined Patent Publication JP-A7-48324 (1995)), etc. have also been developed.

The charge generation substance and the charge transportation substanceare usually used in a manner of being dispersed or dissolved in a binderresin as a binder in order to ensure the mechanical strength of thephotoreceptor. As the resin used for the binder resin, various resinssuch as polymethyl methacrylate resin, polycarbonate resin, andpolyester resin have been proposed.

Performances required for the electrophotographic photoreceptor in theelectrophotographic process are, for example, high surface potentialwhen it is charged, high carrier retention ratio, high lightsensitivity, and less fluctuation of such electric characteristics underall circumstances. Further, it is also demanded that the photosensitivelayer has high film strength, is excellent in wear resistance when usedrepetitively, and high stability of the characteristics throughout theperiod of use, that is, high durability. Further, while thephotosensitive layer is generally formed by coating a coating solutionobtained by dissolving or dispersing the charge generation substance,the charge transportation substance and the binder resin in anappropriate solvent on an electroconductive substrate, it is demandedthat the coating solution is stable both physically and chemically inorder to improve the production efficiency of the photoreceptor.

Among the requirements described above, the durability is a principalsubject of the organic photoreceptor put to practical use. The organicphotoreceptor put to practical use involves a problem of tending tocause scraping of film in the photosensitive layer, and change ofcharacteristics such as lowering of the charge potential and increase ofthe residual potential attributable to electrical change or chemicalchange. They are caused mainly by the insufficient printing resistanceof the photosensitive layer and denaturation and decomposition of anorganic photoconductive material such as the charge transportationsubstance contained in the photosensitive layer by the exposure of thephotoreceptor to light or ozone and nitrogen oxide in the photographicprocess of repeating the steps of forming electrostatic latent images bycharging and exposure, transfer of toner images to a recording mediumand elimination of the toner remaining on the surface of thephotoreceptor by a blade or the like. Accordingly, the role of thebinder resin and the charge transportation substance contained mainly inthe photosensitive layer as the surface layer of the photoreceptor isextremely important.

As the binder resin, among the resins described above,2,2-bis(4-hydoroxyphenol)propane (common name; bisphenol A) or bisphenolA polycarbonate resin using the derivatives as the raw material is usedmainly. However, the electrophotographic photoreceptor using thebisphenol A polycarbonate resin as the binder resin involves thefollowing drawbacks. Since the bisphenol A polycarbonate resin has highcrystallinity, the solution tends to cause gelation and the coatingsolution becomes no more usable in a short period of time in a case offorming a film by coating. Further, in a case of using the film bycoating, when the prepared photoreceptor is used in anelectrophotographic apparatus such as a copying machine since thecrystallized polycarbonate resin sometimes precipitates to the surfaceof the formed film, toner is deposited to convex potions formed bycrystallization of the polycarbonate resin, the toner at the portions isnot completely removed by cleaning but sometimes remains to cause imagedefects due to cleaning failure. Further, the surface of thephotoreceptor tends to be injured and the photosensitive layer tends tobe worn by being rubbed in the developing step or cleaning step in theelectrophotographic apparatus. That is, the durability is low.

In order to solve the drawbacks, various resins have been proposed. Forexample, a copolymer of bisphenol A and other molecules has beenstudied. However no sufficient result has yet been obtained. Further, apolycarbonate resin having a novel specified structure has been proposed(refer to Japanese Examined Patent Publication JP No. 3258537).

Further, in order to compensate the drawback of various resins, use oftwo or more kinds of resins in admixture has been studied. For example,it has been proposed mixing of a bisphenol A polycarbonate resin and abisphenol Z polycarbonate resin (refer to Japanese Examined PatentPublication JP-B2 3-49426 (1991) or mixing of a polycarbonate resinsynthesized from an asymmetric diol and a polycarbonate resinsynthesized from an asymmetric diol (refer to Japanese Unexamined PatentPublication JP-A 6-317917 (1994)). However, for the improvement of thedurability of the photoreceptor, mere improvement for the binder resinand the charge transportation substance independently of each other isstill insufficient and improvement has to be made also taking theinteraction and the compatibility between both of them intoconsideration.

Further, use of a polyarylate resin has been studied. While thepolyarylate resin has a structure similar with the polycarbonate resin,there is a difference among the characteristics of the photoreceptorsusing the resins. While it has been known that the photoreceptor usingthe polyarylate resin is excellent in the mechanical stress, when thepolyarylate resin is used as the binder rein for the chargetransportation layer, it results in a drawback of tending to causelowering of the potential retaining ratio or increase of the residualpotential depending on the structure of the charge transportationsubstance to be used.

On the other hand, as transfer means of the electrophotographicapparatus forming images by electrophotography, a transfer charger thatapplies electric charges to a recording medium to generate an electricfield for attracting the toner on the surface of the photoreceptorthereby transferring toner images on the surface of the photoreceptor tothe recording medium has been used. However, in a case of conductingtransfer by the transfer charger, since the recording medium is merelydeposited electrostatically but not fixed to the photoreceptor at thetransfer portion, this tends to cause a phenomenon referred to astransfer deviation in which toner images can not be transferredaccurately to the recording medium during transfer. While the phenomenonwas less elicited in electrophotographic apparatus of an analog systemtype or at low resolution, the problem of the transfer deviation hasbecome conspicuous accompanied to digitalization and increasingresolution in resent years.

In order to prevent the transfer deviation, a transfer roller has oftenbeen used instead of the transfer charger. In a case of conductingtransfer by using the transfer roller, the transfer roller as a chargingmember of a roller shape constituted with electroconductive rubber orthe like is urged against the photoreceptor from the recording medium onthe side opposite to the contact surface of the photoreceptor, therebyapplying electric charges in a state where the photoreceptor and therecording medium are in press contact with each other. Use of thetransfer roller can prevent the transfer deviation. However, in a casewhere press contact is weak, a portion of the toner images remainswithout being transferred to the recording medium tending to causeblanking where white portions are formed in the images, so that it isnecessary to increase the pressing force. Increase of the pressing forceresults in an additional problem that the scraping amount of thephotosensitive layer increases due to friction between the recordingmedium and the transfer roller. Accordingly, higher mechanical strengthis required for the photoreceptor more and more.

With the requirement, various improvements have been attempted for thephotoreceptor using the polyarylate resin of excellent mechanicalstrength described above. For example, it has been proposed aphotoreceptor using a polyarylate resin and other resin in admixture(refer to Japanese Unexamined Patent Publications JP-A 10-20517 (1998)and JP-A 2000-221722), a photoreceptor in which the surface smoothnessand the stabilization of electric characteristics are made compatible bythe mixing of the polyarylate resin and other resin with a polysiloxane(refer to Japanese Unexamined Patent Publications JP-A 6-89038 (1994)and JP-A 7-114191 (1995)), and a photoreceptor intending tocompatibilize the electric durability and the mechanical durability bythe combination of a polyarylate resin or a polyester resin having astructure similar with the polyarylate resin, and a specific chargetransportation substance (refer to Japanese Unexamined PatentPublications JP-A 10-268535 (1998), and JP-A 2001-215741).

However, it has not yet been obtained such a photoreceptor as capable ofsatisfying both the requirement for further higher mechanical strengthin view of the digitalization and increased resolution of theelectrophotographic apparatus and the requirement for the long timestabilization of electric characteristics in view of the demand for thelonger life of the photoreceptor.

The charge transportation substances must satisfy the followingrequirements:

-   (1) being stable to light and heat;-   (2) being stable to ozone, nitrogen oxides (NOx) and nitric acid    that may be generated in corona discharging on a photoconductor;-   (3) good charge transportation ability;-   (4) being compatible with organic solvents and binder resins;-   (5) being easy to produce and are inexpensive. Though partly    satisfying some of these, however, the charge transportation    substances could not satisfy all of these at high level.

Further, in a case where the charge transportation layer in which acharge transportation substance is dispersed in the binder resin formsthe surface layer of the photoreceptor, particularly high chargetransportation ability is required for the charge transportationsubstance.

An electrophotographic apparatus such as a copying machine or a laserbeam printer comprises a photoreceptor, charging means such as acharging roller for charging a surface of the photoreceptor to apredetermined potential, exposure means for subjecting the chargedsurface of the photoreceptor to exposure to light, developing means forsupplying a developer containing a toner by a magnetic brush or the liketo the surface of the photoreceptor and developing means for developingelectrostatic latent images formed by exposure, transfer means fortransferring the toner images obtained by development onto a recordingmedium, fixing means for fixing the transferred toner images, andcleaning means for removing the toner remaining on the surface of thephotoreceptor by a cleaning blade or the like after the transferringoperation by the transferring means thereby cleaning the surface of thephotoreceptor. In a case where, the photoreceptor is used being mountedon an electrophotographic apparatus, the surface layer of thephotoreceptor is obliged to be partially scraped off by a contact membersuch as a cleaning blade or a charging roller. In a case where thescraping amount of the surface layer of the photoreceptor is large, thecharge retainability of the photoreceptor lowers and images of goodquality can no more be provided for a long period of time. Accordingly,for improving the durability of the electrophotographic apparatus suchas the copying machine or the laser beam printer, it has been demanded aphotoreceptor with high resistance having a surface layer resistant tothe contact member, that is, a surface layer of high printing resistancewith less amount scraped by the contact member.

In order to improve the durability of the photoreceptor by strengtheningthe surface layer, it may be considered to increase the content of thebinder resin in the charge transportation layer as the surface layer.However, as the content of the binder resin in the charge transportationlayer increases, the light responsivity lowers. In a case where thelight responsivity is lowered, that is, the decay speed of the surfacepotential after exposure is slow, since it is used repeatedly in a statewhere the residual potential increases and the surface potential of thephotoreceptor is not sufficiently decayed, the surface charges at theportion to be erased by the exposure are not erased sufficiently toresult in troubles such as early lowering of the image quality. It isknown that the light responsivity depends on the charge mobility of thecharge transportation substance, and the lowering of the lightresponsivity is attributable to the low charge transportation ability ofthe charge transportation substance. That is, along with increase of thecontent of the binder resin, the charge transportation substance in thecharge transportation layer is diluted to further lower the chargetransportation ability of the charge transportation layer to lower thelight responsivity. Accordingly, in order to prevent lowering of thelight responsivity and ensure a sufficient light responsivity, aparticularly high charge transportation ability is required for thecharge transportation substance.

Further, the size has been reduced and the speed has been increased inelectrophotographic apparatus, for example, in digital copying machinesand printers in recent years, and improvement for the sensitivity hasbeen required as the characteristics of the photoreceptor for copingwith the increase of the speed, and high charge transportation abilityhas been demanded more and more as the charge transportation substance.Further, in the high speed electrophotographic process, since the timefrom exposure to development is short, a photoreceptor of high lightresponsivity is demanded. As described above, since the lightresponsivity depends on the charge transportation ability of the chargetransportation substance, a charge transportation substance having ahigher charge transportation ability is demanded also with such a viewpoint.

As the charge transportation substance capable of satisfying such ademand, an enamine compound having a charge mobility higher than that ofthe charge transportation substance described above has been proposed(refer, for example, to Japanese Unexamined Patent Publications JP-A2-51162 (1990), JP-A 6-43674 (1994) and JP-A 10-69107(1998)).

Further, a photoreceptor provided with a high charge transportationability by the incorporation of a polysilane and improved with thechargeability and the film strength by the incorporation of an enaminecompound having a specific structure has been proposed (refer toJapanese Unexamined Patent Publication JP-A 7-134430 (1995)).

On the other hand, the performance such as the durability of thefunction separation type photoreceptor greatly depends on the binderresin itself.

For the binder resin used for the charge transportation layer of thefunction separation type photoreceptor, it has been well-known that abisphenol A polycarbonate resin using 2-bis(4-hydroxyphenol)propane(common name: bisphenol A) represented by the following structuralformula (A) as a raw material provides favorable characteristics in viewof the charge ability, the sensitivity, the residual potential, and therepetitive performance (refer, for example, to Japanese UnexaminedPatent Publication JP-A 5-61215 (1993), page 4).

Further, it has been proposed a technique of improving the durability byincorporating a bisphenol Z polycarbonate resin using1,1-bis(4-hydroxyphenol)cyclohexane (common name: bisphenol Z) as a rawmaterial for the binder resin to the surface of the photosensitive layer(refer, for example, to Japanese Examined Patent Publication JP-No.2844215).

However, the bisphenol A polycarbonate resin used for the photoreceptordescribed, for example, in JP-A 5-61215 involves the following drawbacksthat are attributable to the structural symmetry of bisphenol A.

-   (1) It is poor in the solubility and shows favorable solubility only    to some halogen type organic solvents such as dichloromethane or    1,2-dichloroethane. Since the halogen type organic solvents    described above have low boiling point, when a photoreceptor is    manufactured by using a coating solution prepared with such a    solvent, since the evaporation speed of the solvent is excessively    high, so that the coating film tends to be clouded due to the heat    of evaporation. Further, since the halogen type organic solvent such    as dichloromethane or 1,2-dichloroethane gives a significant effect    such as high toxicity and destruction of ozone layers on an operator    or on the global environment, administration for manufacturing steps    are complicated.-   (2) The resin is soluble partially to other halogen type organic    solvents than those described above such as tetrahydrofurane,    dioxane or cyclohexane, or mixed solvents thereof, but the coating    solutions prepared with the solvents described above are poor in the    aging stability such that they gel within several days after    preparation. Particularly, in a case of manufacturing a    photoreceptor by a manufacturing method such as dip coating, the    coating solution in the coating tank gels to sometimes bring about a    trouble in the production of the photoreceptor.-   (3) Since the inter-molecular attraction force of the resin per se    is strong, the formed coating film is poor in the adhesion and tends    to suffer from crackings form the boundary with other layers.    Further, since the close bondability is poor, the potential barrier    layer formed near the boundary increases, so that charges generated    from the charge generation substance can not be transferred smoothly    as far as the surface of the photosensitive layer and, in a case    where the photoreceptor is used continuously, the difference between    the bright area potential as the surface potential for the exposed    portion and the dark area potential as the surface potential for the    not exposed area is decreased. Accordingly, fogging of formed images    increases in a case of normal development, while the image density    lowers in a case of reversal development, failing to form good    images.-   (4) Since the crystallinity of the resin per see is high, a    polycarbonate resin crystallized to the surface of the film tends to    precipitate to cause protrusion during formation of the coating    film. Accordingly, tailing is caused in the coating film to lower    the productivity. Further, the toner is deposited to the protruded    portions during use of the photoreceptor, which remain without    cleaning tending to cause image defects due to so-called cleaning    failure.-   (5) Since the resin itself lacks in the mechanical strength, the    photoreceptor using the bisphenol A polycarbonate resin as the    binder resin tends to surfer from injuries at the surface by being    frictionally rubbed with a charge roll, a magnetic brush, or a    cleaning blade and is gradually abraded.

Further, as the characteristics of the photoreceptor, it has beendemanded that the light responsivity does not lower even in a case ofuse under a low temperature circumstance and change of characteristicsis small and reliability is high also under various circumstances.However, while the photoreceptor using the bisphenol Z polycarbonateresin as the binder resin described in Japanese Patent No. 2844215 hasfavorable resistance to printing and wear resistance, it has low lightresponsivity and, particularly, the responsivity lowers when used undera low temperature circumstance to bring bout a problem that the qualityof the formed images is deteriorated.

In order to suppress the lowering of the light responsivity under such alow temperature circumstance, it may be considered to use a chargetransportation substance of high charge mobility as described above.However, no sufficient light responsivity can be obtained under the lowtemperature circumstances even using an enamine compound of high chargemobility used for photoreceptors described in JP-A 2-251162, JP-A6-43674, or JP-A 10-69107 above. Further, while the photoreceptordescribed in JP-A 7-134430 is provided with a high charge transportationability by the incorporation of polysilane, the photoreceptor using thepolysilane involves a problem that it is sensible to light exposure andthat various characteristics of the photoreceptor are deteriorated byexposure to light, for example, during maintenance.

In the image forming apparatus forming images by electrophotography,images are formed by way of an electrophotographic process as describedbelow. At first, after supplying a predetermined charge potential fromcharging means provided to the apparatus to the surface of anelectrophotographic photoreceptor (hereinafter simply referred to alsoas “photoreceptor”), thereby charging the surface to a predeterminedpotential, light is irrigated in accordance with image information bythe image exposure means to subject the surface to exposure to lightthereby forming an electrostatic latent image. A developer containing atoner, etc. is supplied from the developing means to the thus formedelectrostatic latent images to visualize the toner images. The thusformed toner images are transferred from the surface of thephotoreceptor to a recording medium such as paper by the transfer meansand then they are fixed by the fixing means.

As the charging means, a charging device of corona charging systemsupplying a charge potential from a wire electrode to the surface of aphotoreceptor by corona discharge is generally used. However, sincecharging is conducted in a no-contact manner in the charging device ofthe corona charging system, the charging efficiency to the surface ofthe photoreceptor is low, and a higher potential compared with thecharge potential on the surface of the photoreceptor has to be appliedto the wire electrode. For example, in order to charge the surface ofthe photoreceptor to negative (−)700 V, a voltage at about negative (−)5kV to negative (−)6 kV has to be applied to the wire electrode.Accordingly, a large power source device is necessary, which bringsabout a problem of increasing the cost. Further, since a great amount ofozone is generated by corona discharge in the charging device of coronacharging system, this also brings about a problem that the materialconstituting the photoreceptor tends to be denatured to degrade imagesor give undesired effects on human bodies.

In view of the above, a contact type charging device for supplying thepotential directly by contacting the charging member to the surface ofthe photoreceptor has been developed in recent years. For example, ithas been proposed a charging device using a composite material in whichan electroconductive material such as electroconductive particles isdispersed in an insulative elastic material is bonded to the surface ofa metal core formed in a roller shape as a charging member (for example,refer to Japanese Unexamined Patent Publications JP-A 58-49960 (1983),JP-A 63-170673 (1988), JP-A 63-149669 (1988), JP-A 64-73365 (1989), andJP-A 1-172857 (1989)). The composite material is formed such that thevolumic resistance is about from 10⁶ to 10⁷ Ωcm and, by the applicationof a voltage to the metal core in a state of contacting the portion ofthe composite material to the surface of the photoreceptor, a potentialis supplied by way of the electroconductive particles to the surface ofthe photoreceptor. As the insulative elastic material, a polymericmaterial such as silicone rubber, polyurethane rubber,ethylene-propylene-diene copolymer (simply referred as EPDM) rubber, ornitrile rubber is used. As the electroconductive particles, carbonpowder, carbon fiber, metal powder, or graphite is used, for example.

Charging by the contact type charging device is conducted, specifically,by gap discharge generated in a minute gap between the charging memberand the photoreceptor. The gap discharge is generated by applying avoltage at a certain value or higher between the charging member and thephotoreceptor. That is, charging is started by applying a voltage abovea charge threshold value voltage as a voltage for generating gapdischarge between the charging member and the photoreceptor.Accordingly, when the photoreceptor is charged, a voltage at apredetermined value equal with or higher than the discharge thresholdvalue voltage, for example, about 1 to 2 kV is applied to the chargingmember.

While the voltage is generally a DC voltage, in a case where only the DCvoltage is applied to the charging member, it is difficult to attain adesired value of the surface potential on the photoreceptor. This isattributable to that the charging becomes not uniform due to thefluctuation of the charging voltage by the fluctuation of the resistancevalue of the charging member caused by the fluctuation of ambienttemperature or humidity of the apparatus or change of the film thicknessof the photosensitive layer caused by scraping of the photoreceptorduring repetitive use. Then, in JP-A 63-149669, JP-A 64-73365, and JP-A1-172857, a vibrating voltage formed by superposing an AC componenthaving a peak-to-peak voltage higher by twice or more the dischargethreshold value voltage to the DC component corresponding to the desiredcharging voltage is applied to the charging member with an aim ofuniform charging. By the application of the vibrating voltage, when thesurface potential on the photoreceptor rises to a value higher than theDC component of the vibrating voltage, since excess charges on thesurface of the photoreceptor can be transferred backwardly from thephotoreceptor to the charging member, it is possible to suppress theeffect by an external factor such as the environment or film scraping ofthe photoreceptor and converge the surface potential of thephotoreceptor to the DC component of the applied vibrating voltage.

On the other hand, as the photoreceptor, inorganic photoreceptors usinginorganic photoconductive materials such as selenium, cadmium sulfideand zinc oxide have been used generally so far. Further, as the organicphotoreceptor using the organic photoconductive material, those using aphotoconductive polymer typically represented by poly(N-vinylcarbozole),those using an organic photoconductive material of low molecular weightsuch as 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, as well as acombination of such an organic photoconductive material with variouskinds of dyes and pigments are known.

Since the organic photoreceptor has a good film forming property for thephotosensitive layer and can be produced by coating, it has an advantagethat the productivity is extremely high and that it is inexpensive.Further, it also has an advantage that the light sensitive wavelengthregion can be controlled optionally by properly selecting the dyes,pigments, etc. to be used. Since the organic photoreceptors have manyadvantages as described above, they have been studied extensively.Particularly, the sensitivity and the durability which are concernedwith the drawbacks on the existent organic photoreceptor have beenremarkably improved recently by the development of a function separationtype photoreceptor having a photosensitive layer in which a chargegeneration layer using an organic photoconductive dye or pigment as acharge generation substance and a charge transportation layer containinga photoconductive polymer or an organic photoconductive material of lowmolecular weight as a charge transportation substance are stacked, andthe organic photoreceptor has become predominant in theelectrophotographic photoreceptors.

However, since defects such as agglomerated portions of the chargetransportation substance and the charge generation substance are tendedto occur in the organic photoreceptor, when charging is conducted byusing the contact type charging device described above to the organicphotoreceptor, it results in the following problems. That is, in thecontact type charging device, since a high electric field is appliedbeing concentrated to the contact portion between the photosensitivelayer and the charging member, charges from the charging member areconcentrated to the defective portions, if any, in the photosensitivelayer to charge the photosensitive layer not uniformly to cause spotwiseor stripe-like image defects. Further, in a case where charges areconcentrated remarkably from the charging member to the defectiveportions, leakage occurs to the photosensitive layer and thephotosensitive layer itself suffers from dielectric breakdown andsubsequent formation of normal images can no more be conducted. Further,the charging member itself undergoes damages by the leak current and itcan be used no more.

As the technique for solving the problem caused by the leakage in thephotosensitive layer, it has been proposed, for example, coating acoating solution divisionally for plural times upon forming the chargetransportation layer by coating, thereby decreasing the overlap of thedefects in the direction of the film thickness of the chargetransportation layer (refer to Japanese Unexamined Patent PublicationJP-A 10-10761 (1998)), and suppression of agglomeration of the chargetransportation substance by decreasing the amount of the chargetransportation substance to the binder resin in the photosensitive layer(refer to Japanese Unexamined Patent Publication JP-A 2001-56595).

Further, while corona discharge or gap discharge is utilized forcharging the photoreceptor as described above, the organic photoreceptorinvolves a problem that the charge transportation substance tends tocause decomposition or degradation of the charge transportationsubstance by active gases such as ozone or NOx generated by thedischarge, tending to degrade the surface of the photosensitive layerand electric characteristics such as the chargeability, the sensitivityand the responsivity are lowered due to the repetitive use to degradethe picture quality. In a case of using the contact type charging deviceas the charging device, since discharge occurs near the surface of thephotoreceptor, degradation on the surface of the photoreceptor caused bydischarge is more serious than in a case of using the charging device ofcorona discharging system. Further, in a case of applying the vibratingvoltage to the charging member for uniform charging, discharge occursalso upon reversed transfer of the excess charges on the surface of thephotoreceptor to the charging member as described above and thedischarge occurs more frequently compared with the case of applying onlythe DC voltage, degradation of the surface of the photoreceptor is moreconspicuous.

Further, in a case of using the contact type charging device, since thesurface of the photosensitive layer is scraped by the contact with thecharging member, the photosensitive layer suffers from more wearing dueto repetitive use compared with the case of using the charging device ofcorona charging system. In a case where the amount of wear of thephotosensitive layer is large, the charge retainability is lowered andimages of high quality can no more be provided. Further, when thethickness of the photosensitive layer is thus decreased, dielectricbreakdown of the photosensitive layer described above tends to generatefurther.

For suppressing the degradation and wear on the surface of thephotosensitive layer, it has been proposed to use a chargetransportation layer formed by polymerizing a hole transporting compoundhaving two or more chain polymerizable functional groups in oneidentical molecule. According to the technique, since the portion thatfunctions as the charge transportation substance is contained in thepolymerized hole transferring compound and does not agglomerate,occurrence of defects to the photosensitive layer can be suppressed(refer to Japanese Unexamined Patent Publication JP-A 2001-166502).

In the technique described in JP-A 10-10761, since the occurrence ofdefects per se can not be suppressed, dielectric breakdown of thephotosensitive layer can not be avoided. Further, since it is necessaryto repeat the step of coating the coating solution and the step ofdrying the same for forming the charge transportation layer in thistechnique, the production efficiency is poor.

Further, in the technique described in Japanese Unexamined PatentPublication JP-A 2001-56595, the sensitivity and the responsivity of thephotoreceptor are insufficient and, in a case of a high speedelectrophotographic process, image defects such as background stains andlowering of the image density occur.

Further, in the technique described in Japanese Unexamined PatentPublication JP-A2001-166502, it is necessary to polymerize the holetransferring compound by radiation rays or the like in order to form thecharge transportation layer of the photoreceptor and this is difficultto manufacture by the existent manufacturing apparatus.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an electrophotographicphotoreceptor of high durability, excellent in mechanical strength,capable of enduring increase of mechanical stress accompanied todigitalization and increasing resolution of the electrophotographicapparatus, and capable of providing favorable electric characteristicsstably for a long period of time, by the combination of a specifiedresin excellent in the mechanical strength and a specified chargetransportation substance excellent in the high charge transportationability, a process cartridge having the electrophotographicphotoreceptor and not requiring exchange for a long period of time, andan electrophotographic apparatus capable of having transfer meanssuitable to the increasing resolution.

Another object of the invention is to provide an electrophotographicphotoreceptor having high charge potential and charge retainability,high sensitivity and sufficient light responsivity, and excellent indurability with no deterioration of the characteristics even when it isused under a low temperature circumstance or in a high speedelectrophotographic process or exposed to light, having high reliabilityand favorable productivity, as well as an image forming apparatus havingthe same.

Further another object of the invention is to provide an image formingmethod and an image forming apparatus with no dielectric breakdown for aphotosensitive layer caused by leakage upon charging by contacting acharging member to the electrophotographic photoreceptor and capable ofstably providing high quality images with no image defects caused byleakage for a long period of time.

The invention provides an electrophotographic photoreceptor comprising:

an electroconductive substrate formed of an electroconductive material;and

a photosensitive layer disposed on the electroconductive substrate andcontaining a polyarylate resin having a structural unit represented bythe following general formula (1) and an enamine compound represented bythe following general formula (2):

(in which X¹ represents a single bond or —CR⁵R⁶—. R⁵ and R⁶ eachrepresents a hydrogen atom, a halogen atom, an alkyl group which mayhave a substituent, or an aryl group which may have a substituent.Further, R⁵ and R⁶ may join to each other to form a ring structure. R¹,R², R³, and R⁴ each represents a hydrogen atom, a halogen atom, an alkylgroup which may have a substituent or an aryl group which may have asubstituent. R⁷, R⁸, R⁹, and R¹⁰ each represents a hydrogen atom, ahalogen atom, or an alkyl group which may have a substituent or an arylgroup which may have a substituent)

(in which Ar¹ and Ar² each represents an aryl group which may have asubstituent or a heterocyclic group which may have a substituent. Ar³represents an aryl group which may have a substituent, a heterocyclicgroup which may have a substituent, an aralkyl group which may have asubstituent, or an alkyl group which may have a substituent. Ar⁴ and Ar⁵each represents a hydrogen atom, an aryl group which may have asubstituent, a heterocyclic group which may have a substituent, anaralkyl group which may have a substituent, or an alkyl group which mayhave a substituent. However, both Ar⁴ and Ar⁵ do not form the hydrogenatoms. Ar⁴ and Ar⁵ may join to each other by way of an atom or an atomicgroup to form a ring structure. “a” represents an alkyl group which mayhave a substituent, an alkoxy group which may have a substituent, adialkylamino group which may have a substituent, an aryl group which mayhave a substituent, a halogen atom or a hydrogen atom, and m representsan integer of 1 to 6. In a case where m is 2 or more, plural a may beidentical or different with each other or may join to each other to forma ring structure. R¹¹ represents a hydrogen atom, a halogen atom, or analkyl group which may have a substituent. R¹², R¹³, and R¹⁴ eachrepresents a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, a heterocyclic group whichmay have a substituent, or an aralkyl group which may have asubstituent. n represents an integer of 0 to 3 and in a case where n is2 or 3, plural R¹² may be identical or different with each other, andplural R¹³ may be identical or different with each other. However, in acase where n represents 0, Ar³ represents a heterocyclic ring which mayhave a substituent).

According to the invention, the photosensitive layer disposed on theelectroconductive substrate of the electrophotographic photoreceptorcontains a polyarylate resin having a structural unit represented by thegeneral formula (1) and an enamine compound represented by the generalformula (2). The polyarylate resin having the structural unitrepresented by the general formula (1) is excellent in mechanicalstrength. In the process of electrophotograpny, the photosensitive layeris scraped and worn by a contacting member used upon removing the tonerremained on the surface of the photoreceptor during or aftertransferring the toner images on the surface of the photoreceptorobtained by developing electrostatic latent images to a recordingmedium. However, since the photosensitive layer disposed on theelectrophotographic photoreceptor of the invention contains, asdescribed above, the polyarylate resin having a structural unitrepresented by the general formula (1) excellent in the mechanicalstrength, it has excellent wear resistance with little wear amount ofthe photosensitive layer, and with less change of the characteristicscaused by scraping of the film of the photosensitive layer. Further,since the enamine compound represented by the general formula (2) hasexcellent compatibility with the polyarylate resin having a structuralunit represented by the general formula (1), and has a high chargemobility, in a case where the photosensitive layer contains thepolyarylate resin having the structural unit represented by the generalformula (1), it is possible obtain an electrophotographic photoreceptorhaving high charge potential, high sensitivity and sufficient lightresponsivity, and not suffering from the lowering of the electriccharacteristics even after repetitive use. Accordingly, by incorporatingthe polyarylate resin having the structural unit represented by thegeneral formula (1) and the enamine compound represented by the generalformula (2) in combination in the photosensitive layer, it is possibleto obtain an electrophotographic photoreceptor of high durability, whichis excellent in mechanical strength, endurable to the increase ofmechanical stresses along with digitalization and increased resolutionof electrophotographic apparatus, as well as capable of providingsatisfactory electric characteristics stably over a long period of time.

Further, the invention is characterized in that the photosensitive layercontains a polyarylate resin having a structural unit represented by thegeneral formula (1), in which X¹ is —CR⁵R⁶—, each of R¹, R², R³, R⁴, R⁵,and R⁶ is a methyl group and each of R⁷, R⁸, R⁹, and R¹⁰ is a hydrogenatom.

According to the invention, the photosensitive layer contains apolyarylate resin having a structural unit in which X¹ is —CR⁵R⁶—, eachof R¹, R², R³, R⁴, R⁵, and R⁶ is a methyl group and each of R⁷, R⁸, R⁹,and R¹⁰ is a hydrogen atom. Since the polyarylate resin is excellent inthe solubility to a solvent, it can improve the stability of the coatingsolution when forming a photosensitive layer by coating. Accordingly,production efficiency of the electrophotographic photoreceptor can beimproved.

Further, the invention is characterized in that the enamine compoundrepresented by the following formula (2) is an enamine compoundrepresented by the following general formula (3).

(wherein b, c and d each represent an optionally-substituted alkylgroup, an optionally-substituted alkoxy group, an optionally-substituteddialkylamino group, an optionally-substituted aryl group, a halogenatom, or a hydrogen atom; i, k and j each indicate an integer of from 1to 5; when i is 2 or more, then the “b”s may be the same or differentand may bond to each other to form a cyclic structure; when k is 2 ormore, then the “c”s may be the same or different and may bond to eachother to form a cyclic structure; and when j is 2 or more, then the “d”smay be the same or different and may bond to each other to form a cyclicstructure; Ar⁴, Ar⁵, “a” and “m” represent the same as those defined informula (1)).

According to the invention, since the enamine compound represented bythe general formula (2) is an enamine compound represented by thegeneral formula (3), it has a particularly high charge mobility. Namely,since the photosensitive layer has an enamine compound represented bythe following general formula (3) having a particularly high chargemobility, it is possible to obtain an electrophotographic body havinghigh charge potential, high sensitivity and sufficient responsivity andexcellent durability, and with high reliability without degradation ofthe characteristics even when used in a high speed electrophotographicprocess.

Further, the invention is characterized in that the photosensitive layerhas a stacked structure in which a charge generation layer containing acharge generation substance and a charge transportation layer containingthe charge transportation substance containing the enamine compoundrepresented by the general formula (2) and a polyarylate resin havingthe structural unit represented by the general formula (1) are stackedin this order to the outside from the electroconductive substrate.

According to the invention, a photosensitive layer has a stackedstructure in which a charge generation layer containing a chargegeneration substance and a charge transportation layer containing thecharge transportation substance containing the enamine compoundrepresented by the general formula (2) and a polyarylate resin havingthe structural unit represented by the general formula (1) are stackedin this order to the outside from the electroconductive substrate. Sincea charge generating function and a charge transportation function areshared on separate layers respectively, materials suitable to respectivecharge generating function and charge transportation function can beselected, an electrophotographic photoreceptor having higher sensitivityand higher durability in which stability upon repetitive use is furtherimproved can be obtained. In a photosensitive layer having such astacked structure, although the charge transportation layer is scrapedand worn by a contact member to be used upon removing a toner remainedon the surface of the photoreceptor during or after the transfer oftoner images on the surface of the photoreceptor obtained by developingelectrostatic latent images to a recording medium, since the chargetransportation layer disposed on the electrophotographic sensitive bodyof the invention contains the polyarylate resin having a structural unitrepresented by the general formula (1) having excellent mechanicalstrength as described above, the wear amount of the chargetransportation layer is small. Accordingly, an electrophotographicphotoreceptor excellent in wear resistance and with less change in thecharacteristics which is caused by film scraping of the photosensitivelayer can be obtained.

Further, the invention is characterized in that an intermediate layer isdisposed between the electroconductive substrate and the photosensitivelayer.

According to the invention, the intermediate layer is disposed betweenthe electroconductive substrate and the photosensitive layer. With sucha constitution, since the injection of charges from theelectroconductive substrate to the photosensitive layer can beprevented, deterioration of the chargeability of the photosensitivelayer can be prevented, reduction of surface charges in a portion otherthan portions to be erased by exposure can be suppressed, and occurrenceof defects such as fogging on images can be prevented. Further, sincethe defects on the surface of the electroconductive substrate can becovered to provide a uniform surface, the film-forming property of thephotosensitive layer can be enhanced. Further, peeling of thephotosensitive layer from the electroconductive substrate can besuppressed, to improve adhesion between the electroconductive substrateand the photosensitive layer.

Further, the invention provides a process cartridge attachable to anddetachable from an electrophotographic apparatus main body, integrallycomprising:

the electrophotographic photoreceptor mentioned above; and

at least one of means selected from the group consisting of chargingmeans for charging the electrophotographic photoreceptor, developingmeans for developing electrostatic latent images formed by subjectingthe electrophotographic photoreceptor to exposure to light, and cleaningmeans for cleaning the electrophotographic photoreceptor aftertransferring the developed images onto a recording medium.

According to the invention, the process cartridge attachable to anddetachable from an electrophotographic apparatus main body integrallycomprises an electrophotographic photoreceptor of the invention and atleast one of means selected from the group consisting of charging means,developing means, and cleaning means. With such a constitution, since itis not necessary to separately attach or detach the electrophotographicphotoreceptor and at least one of means selected from the groupconsisting of charging means, developing means, and cleaning meansindividually to and from the main body of the electrophogographicapparatus, the process cartridge can be attached or detached easily toor from the main body of the electrophotographic apparatus. In addition,as described above, since the electrophotographic photoreceptor of theinvention equipped to the process cartridge of the invention isexcellent in the mechanical strength, endurable to the increase ofmechanical stresses along with digitalization and increased resolutionof the electrophotographic apparatuses, as well as capable of providingsufficient electric characteristics stably for a long period of time, itis possible to obtain a stress cartridge requiring no exchange over along period of time.

Further, the invention provides an electrophotographic apparatuscomprising:

the electrophotographic photoreceptor mentioned above;

charging means for charging the electrophotographic photoreceptor;

exposure means for subjecting the charged electrophotographicphotoreceptor to exposure to light;

developing means for developing electrostatic latent images formed bythe exposure to light; and

transfer means for transferring the developed images onto a recordingmedium.

According to the invention, the electrophotographic apparatus comprisesthe electrophotographic photoreceptor mentioned above, the chargingmeans, the exposure means, the developing means and the transferringmeans. As described above, the electrophotographic photoreceptor of theinvention is excellent in the mechanical strength, capable of enduringincrease of mechanical stresses accompanying digitalization andincreased resolution of the electrophotographic apparatuses, and canprovide sufficient electric characteristics stably for a long period oftime. Accordingly, as described above, an electrophotographic apparatuswith high reliability capable of providing high quality images over along period of time can be provided by incorporating theelectrophotographic photoreceptor of the invention.

The invention is characterized in that the transfer means transferdeveloped images onto the recording medium by press contacting theelectrophotographic photoreceptor and the recoding medium.

According to the invention, the transfer means transfer developed imagesonto the recording medium by press contacting the electrophotographicphotoreceptor and the recording medium. In a case of using such transfermeans, the transfer means are pressed against the electroconductivephotoreceptor. Since the photosensitive layer of the electrophotographicphotoreceptor of the invention contains a polyarylate resin having astructural unit represented by the general formula (1) excellent in themechanical strength, as described above, the wear amount of thephotosensitive layer is small, and defects on the surface of thephotosensitive layer are scarcely caused. Accordingly, since pressingforce by the transfer means can be increased to improve the transferefficiency to the recording medium, there it is possible to obtain anelectrophotographic apparatus of high reliability capable of providinghigh quality images with less transfer deviation, with less imagedefects such as whitening or blanking.

Further, the invention provides an electrophotographic photoreceptorcomprising:

an electroconductive substrate formed of an electroconductive material;and

a photosensitive layer disposed on the electroconductive substrate andcontaining a polycarbonate resin having an asymmetric diol ingredientand an enamine compound represented by the following general formula(2):

(in which Ar¹ and Ar² each represents an aryl group which may have asubstituent or a heterocyclic group which may have a substituent. Ar³represents an aryl group which may have a substituent, a heterocyclicgroup which may have a substituent, an aralkyl group which may have asubstituent, or an alkyl group which may have a substituent. Ar⁴ and Ar⁵each represents a hydrogen atom, an aryl group which may have asubstituent, a heterocyclic group which may have a substituent, anaralkyl group which may have a substituent, or an alkyl group which mayhave a substituent. However, both Ar⁴ and Ar⁵ do not form the hydrogenatoms. Ar⁴ and Ar⁵ may join to each other by way of an atom or an atomicgroup to form a ring structure. “a” represents an alkyl group which mayhave a substituent, an alkoxy group which may have a substituent, adialkylamino group which may have a substituent, an aryl group which mayhave a substituent, a halogen atom or a hydrogen atom, and m representsan integer of 1 to 6. In a case where m is 2 or more, plural a may beidentical or different with each other or may join to each other to forma ring structure. R¹¹ represents a hydrogen atom, a halogen atom, or analkyl group which may have a substituent. R¹², R¹³, and R¹⁴ eachrepresents a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, a heterocyclic group whichmay have a substituent, or an aralkyl group which may have asubstituent. n represents an integer of 0 to 3 and in a case where n is2 or 3, plural R¹² may be identical or different with each other, andplural R¹³ may be identical or different with each other. However, in acase where n represents 0, Ar³ represents a heterocyclic ring which mayhave a substituent).

According to the invention, the photosensitive layer disposed on theelectroconductive substrate of the electroconductive photoreceptorcontains a polycarbonate resin having an asymmetric diol ingredient andan enamine compound represented by the general formula (2). Since theenamine compound represented by the general formula (2) has a highcharge mobility, an electrophotographic photoreceptor having high chargepotential and charge retainability, high sensitivity and sufficientlight responsivity, and excellent in durability can be provided, byincorporating the enamine compound represented by the general formula(2) as a charge transportation substance in the photosensitive layer.Further, since high charge transportation ability can be attainedwithout incorporating a polysilane in the photosensitive layer, anelectrophotographic photoreceptor of high reliability with nodegradation of characteristics by exposure to light can be obtained. Inaddition, since the polycarbonate resin having the asymmetric diolingredient contained in the photosensitive layer exhibits highsolubility to a solvent irrespective that the solvent is a halogen typeorganic solvent or a non-halogen type organic solvent, even when acoating solution is prepared by using the non-halogen type organicsolvent upon forming the photosensitive layer by coating, the coatingsolution containing the polycarbonate resin having the asymmetric diolingredient does not gelate, has satisfactory film-forming property andexcellent stability, and does not gelate even after lapse of severaldays from the preparation. The productivity of the electrophotographicphotoreceptor can be improved by using such a coating solution. Further,since the polycarbonate resin having the asymmetric diol ingredient isexcellent in the mechanical strength, it can suppress occurrence ofinjuries on the surface of the photosensitive layer, reduce the filmreduction amount of the photosensitive layer, and decrease the change ofthe characteristics caused by the wear of the photosensitive layer. Onthe other hand, in a case where the photosensitive layer is incorporatedwith the polycarbonate resin having the asymmetric diol ingredient,characteristics such as light responsivity is sometimes deteriorated.However, since the photosensitive layer disposed on theelectrophotographic photoreceptor of the invention contains the enaminecompound represented by the general formula (2) having high chargemobility as described above, the characteristics are not deterioratedeven when it is used under a low temperature circumstance or in a highspeed electrophotographic process. Accordingly, by incorporating theenamine compound represented by the general formula (2) and thepolycarbonate resin having the asymmetric diol ingredient in combinationto the photosensitive layer, it is possible to obtain anelectrophotographic photoreceptor having high charge potential andcharge retainability, high sensitivity and satisfactory lightresponsivity, excellent in durability, having high reliability withoutlowering of the characteristics even when used in an electrophotographicprocess under a low temperature circumstance or in a high speedelectrophotographic process, or when exposed to light and havingsatisfactory productivity.

Further, the invention is characterized in that the enamine compoundrepresented by the following formula (2) is an enamine compoundrepresented by the following general formula (3).

(wherein b, c and d each represent an optionally-substituted alkylgroup, an optionally-substituted alkoxy group, an optionally-substituteddialkylamino group, an optionally-substituted aryl group, a halogenatom, or a hydrogen atom; i, k and j each indicate an integer of from 1to 5; when i is 2 or more, then the “b”s may be the same or differentand may bond to each other to form a cyclic structure; when k is 2 ormore, then the “c”s may be the same or different and may bond to eachother to form a cyclic structure; and when j is 2 or more, then the “d”smay be the same or different and may bond to each other to form a cyclicstructure; Ar⁴, Ar⁵, “a” and “m” represent the same as those defined informula (1)).

According to the invention, since the photosensitive layer contains theenamine compound represented by the general formula (3) havingparticularly high charge mobility among the enamine compoundsrepresented by the general formula (2), an electrophotographicphotoreceptor showing higher light responsivity can be obtained.Further, since the enamine compound represented by the general formula(3) can be synthesized relatively easily at high yield among the enaminecompounds represented by the general formula (2), it can be producedinexpensively. Accordingly, the electrophotographic photoreceptor of theinvention having excellent characteristics as described above can beproduced at a low production cost.

Further, the invention is characterized in that the polycarbonate resinhaving the asymmetric diol ingredient is a polycarbonate resin having astructural unit containing an asymmetric diol ingredient represented bythe following general formula (II).

(where R²¹, R²², R²³, R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸ each represents ahydrogen atom, a halogen atom, an alkyl group which may have asubstituent, an aryl group which may have a substituent, or an alkoxygroup which may have a substituent. R²⁹ and R³⁰ each represents ahydrogen atom, a halogen atom, an alkyl group which may have asubstituent, or an aryl group which may have a substituent, providingthat R²⁹ and R³⁰ are different from each other or join with each otherto form a ring structure).

According to the invention, the polycarbonate resin having theasymmetric diol ingredient is a polycarbonate resin having a structuralunit containing an asymmetric diol ingredient represented by the generalformula (II), has a bulky substituent in the main chain, and hasparticularly high mechanical strength since the packing density of theresin per se is high. Accordingly, it is possible to obtain anelectrophotographic photoreceptor having excellent durability, with lessoccurrence of injuries on the surface of the photosensitive layer, andwith small film reduction amount of the photosensitive layer.

Further, the invention is characterized in that the polycarbonate resinhaving the asymmetric diol ingredient further has a siloxane structure.

According to the invention, since the polycarbonate resin having theasymmetric diol ingredient further has a siloxane structure, the surfacefriction coefficient of the photosensitive layer is reduced to improvethe slidability. Accordingly, since the toner adhered on the surface ofthe photosensitive layer can be peeled easily, the transfer efficiencyupon transfer of toner images formed on the surface of thephotosensitive layer to a recording medium and cleaning property on thesurface of the photosensitive layer after transfer are improved, so thatsatisfactory images can be obtained. In addition, since paper powdercausing injuries on the surface of the photosensitive layer can bepeeled easily, defects are scarcely formed on the surface of thephotosensitive layer. Further, even in a case where a cleaning blade isslid upon removing the toner remained on the surface of thephotosensitive layer after transfer, since friction and vibrationaccompanying the physical contact of the cleaning head with the surfaceof the photosensitive layer, noises so-called “ringing” less occur.

The invention is characterized in that the photosensitive layer containsan oxotitanium phthalocyanine.

According to the invention, the photosensitive layer further contains anoxotitanium phthalocyanine. Since the oxotitanium phthalocyanine is acharge generation substance having high charge generating efficientlyand charge injecting efficiency, it generates a large quantity ofcharges by absorption of light, and efficiently injects the generatedcharges to the charge transportation substance without accumulationtherein. Further, as described above since the photosensitive layercontains the enamine compound represented by the general formula (2)having high charge mobility, as a charge transportation substance,charges generated by the charge generation substance by light absorptionare injected efficiency to the charge transportation substance andtransferred smoothly. Accordingly, by incorporating the enamine compoundrepresented by the general formula (2) and the oxotitaniumphthalocyanine to the photosensitive layer, an electrophotographicphotoreceptor having high sensitivity and high resolution can beobtained. Further, since the oxotitanium phthaloycanine has the maximumabsorption peak in the wavelength region of a laser light irradiatedfrom an infrared ray laser, high quality images can be provided in adigital image forming apparatus having an infrared laser as a lightsource for exposure by using the electrophotographic photoreceptor ofthe invention.

Further, the invention is characterized in that the photoreceptor has astacked structure composed of at least a charge generation layercontaining a charge generation substance and a charge transportationlayer containing a charge transportation substance,

the charge transportation substance contains an enamine compoundrepresented by the general formula (2), and

at least the charge transportation layer among the charge generationlayer and the charge transportation layer contains a polycarbonate resinhaving the asymmetric diol ingredient.

According to the invention, the photosensitive layer has a stackedstructure of at least a charge generation layer containing a chargegeneration substance and a charge transportation layer containing acharge transportation substance containing an enamine compoundrepresented by the general formula (2). By sharing the charge generatingfunction and the charge transporting function respectively, to separatelayers, since materials suitable to respective charge generatingfunction and the charge transporting function can be selected, anelectrophotographic photoreceptor having higher sensitivity, increasedstability upon repetitive use and higher durability can be obtained.Further, at least the charge transportation layer among the chargegeneration layer and the charge transportation layer contains thepolycarbonate resin having the asymmetric diol ingredient, productivityof the electrophotographic photoreceptor can be improved. In particular,in a case where the charge transportation layer incorporating thepolycarbonate resin having the asymmetric diol ingredient is used as asurface layer of the photosensitive layer, occurrence of injuries on thesurface of the photosensitive layer can be suppressed, film reductionamount of the photosensitive layer can be reduced, and change ofcharacteristics of the photosensitive layer caused by wear of thephotosensitive layer can be reduced.

Further, the invention is characterized in that the photosensitive layerhas a stacked structure in which the charge generation layer and thecharge transportation layer containing a binder resin containing apolycarbonate resin having the asymmetric diol ingredient are stacked inthis order to the outside from the electroconductive substrate, in which

the ratio A/B for the charge transportation substance (A) and binderresin (B) in the charge transportation layer is from 10/12 to 10/30 byweight ratio.

According to the invention, the photosensitive layer has a stackedstructure in which the charge generation layer containing the chargegeneration substances and the charge transportation layer containing thecharge transportation substance having the enamine compound representedby the general formula (2) and a binder resin containing a polycarbonateresin having the asymmetric diol ingredient are stacked in this order tothe outside from the electroconductive substrate, in which the ratio A/Bfor the charge transportation substance (A) and binder resin (B) in thecharge transportation layer is from 10/12 to 10/30 by weight ratio.Since the charge transportation substance contained in the chargetransportation layer as a surface layer of the photosensitive layercontains the enamine compound of high charge mobility, represented bythe general formula (2) as described above, the light responsivity canbe maintained even in a case where the ratio A/B is defined as 10/12 to10/30, and a binder resin is added at a ratio higher than that in a caseof using a charge transportation substance known so far. Namely, thebinder resin containing the polycarbonate resin having the asymmetricdiol ingredient can be contained at a high concentration withoutlowering the light responsivity in the charge transportation layer.Accordingly, since friction resistance of the charge transportationlayer is improved, and change of the characteristics due to the wear ofthe photosensitive layer can be suppressed, durability of theelectropohotographic photoreceptor can be improved. Further, since thepolycarbonate resin having the asymmetric diol ingredient contained inthe photosensitive layer exhibits high solubility to a solventirrespective that the solvent is a halogen type organic solvent or anon-halogen type organic solvent as described above, even in a case ofadding the binder resin at such high ratio, the coating solution isstable without gelation, so that an electrophotographic photoreceptorcan be produced efficiently for a long period of time.

Further, the invention provides an image forming apparatus comprising:

the electrophotographic photoreceptor of the invention;

charging means for charging the electrophotographic photoreceptor;

exposure means for subjecting the charged electrophotographicphotoreceptor to exposure to light; and

developing means for developing electrostatic latent images formed byexposure.

According to the invention, the image-forming apparatus comprises theelectrophotographic photoreceptor, the charging means, the exposuremeans, and the developing means. Since the electrophotographicphotoreceptor of the invention has, as described above, high chargepotential and high charge retainability, high sensitive and satisfactorylight responsivity is excellent in durability, with no deteriorated ofthe characteristics even in a case where it is used under a lowtemperature circumstance or in a high speed electrophotographic process,a highly reliable image-forming apparatus capable of providing highquality images under various circumstances for a long period of time canbe obtained. In addition, since the characteristics of the photographicphotoreceptor of the invention are not deteriorated by exposure tolight, deterioration of image quality by exposure of theelectrophotographic photoreceptor to light upon maintenance or the likecan be prevented to improve the reliability of the image-formingapparatus.

Further, the invention provides a method of forming images, including astep of preparing an electrophotographic photoreceptor, a contactcharging step of conducting charging by bringing a charging member intocontact with the obtained electrophotographic photoreceptor, animagewise exposure step of conducting imagewise exposure to the chargedelectrophotographic photoreceptor, thereby forming electrostatic latentimages, and a developing step of developing the formed electrostaticlatent images, wherein, in the step of preparing the electrophotographicsensitive body, an electroconductive substrate formed of anelectroconductive material is prepared, and a photosensitive layercontaining an enamine compound represented by the following generalformula (2) and a binder resin is formed on the electroconductivesubstrate.

(in which Ar¹ and Ar² each represents an aryl group which may have asubstituent or a heterocyclic group which may have a substituent. Ar³represents an aryl group which may have a substituent, a heterocyclicgroup which may have a substituent, an aralkyl group which may have asubstituent, or an alkyl group which may have a substituent. Ar⁴ and Ar⁵each represents a hydrogen atom, an aryl group which may have asubstituent, a heterocyclic group which may have a substituent, anaralkyl group which may have a substituent, or an alkyl group which mayhave a substituent. However, both Ar⁴ and Ar⁵ do not form the hydrogenatoms. Ar⁴ and Ar⁵ may join to each other by way of an atom or an atomicgroup to form a ring structure. “a” represents an alkyl group which mayhave a substituent, an alkoxy group which may have a substituent, adialkylamino group which may have a substituent, an aryl group which mayhave a substituent, a halogen atom or a hydrogen atom, and m representsan integer of 1 to 6. In a case where m is 2 or more, plural a may beidentical or different with each other or may join to each other to forma ring structure. R¹¹ represents a hydrogen atom, a halogen atom, or analkyl group which may have a substituent. R¹², R¹³, and R¹⁴ eachrepresents a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, a heterocyclic group whichmay have a substituent, or an aralkyl group which may have asubstituent. n represents an integer of 0 to 3 and in a case where n is2 or 3, plural R¹² may be identical or different with each other, andplural R¹³ may be identical or different with each other. However, in acase where n represents 0, Ar³ represents a heterocyclic ring which mayhave a substituent).

Further, the invention is characterized in that the enamine compoundrepresented by the following formula (2) is an enamine compoundrepresented by the following general formula (3).

(wherein b, c and d each represent an optionally-substituted alkylgroup, an optionally-substituted alkoxy group, an optionally-substituteddialkylamino group, an optionally-substituted aryl group, a halogenatom, or a hydrogen atom; i, k and j each indicate an integer of from 1to 5; when i is 2 or more, then the “b”s may be the same or differentand may bond to each other to form a cyclic structure; when k is 2 ormore, then the “c” s may be the same or different and may bond to eachother to form a cyclic structure; and when j is 2 or more, then the “d”smay be the same or different and may bond to each other to form a cyclicstructure; Ar⁴, Ar⁵, “a” and “m” represent the same as those defined informula (2).

The invention is characterized in that the ratio A/B for the enaminecompound (A) represented by the general formula (2) and the binder resin(B) in the photosensitive layer is from 10/12 to 10/30 by weight ratio.

The invention provides an image forming apparatus comprising:

an electrophotographic photoreceptor;

contact charging means having a charging member, for conducting chargingby bringing the charging member into contact with theelectrophotographic photoreceptor;

imagewise exposure means for conducting imagewise exposure to thecharged electrophotographic photoreceptor thereby forming electrostaticlatent images; and

developing means for developing the formed electrostatic latent images,

the electrophotographic photoreceptor including:

an electroconductive substrate formed of an electroconductive materialand a photosensitive layer disposed on the electroconductive substrateand containing an elamine compound represented by the general formula(2) and a binder resin.

Further, the invention is characterized in that the enamine compoundrepresented by the general formula (2) is an enamine compoundrepresented by the general formula (3).

The invention is characterized in that the ratio A/B for the enaminecompound (A) represented by the general formula (2) and the binder resin(B) in the photosensitive layer is from 10/12 to 10/30 by weight ratio.

Further, the invention is characterized in that the charging member hasa roller-like shape.

Further, the invention is characterized in that the charging member hasa brush-like shape.

According to the invention, images are formed by forming aphotosensitive layer containing the enamine compound represented by thegeneral formula (2) and the binder resin to form an electrophotographicphotoreceptor, and after contacting the charging member to the obtainedelectrophotographic photoreceptor thereby conducting charging, imagewiseexposure is conducted to form electrostatic latent images and the formedelectrostatic latent images are developed. Since the enamine compoundrepresented by the general formula (2) is a charge transportationsubstance having a high charge mobility, it has high chargeability,sensitivity and responsivity, so that an electrophotographicphotoreceptor with no deterioration of the electric characteristics evenwhen used repetitively can be obtained. Further, since the enaminecompound represented by the general formula (2) is excellent incompatibility with the binder resin and in the solubility to thesolvent, it is dispersed uniformly in the binder resin withoutagglomeration, and when forming the photosensitive layer by coating, itdissolves uniformly in the coating solution without agglomeration.Accordingly, the electrophotographic photoreceptor has a uniformphotosensitive layer with scarce injuries. Namely, by incorporating theenamine compound represented by the general formula (2) as a chargetransportation substance in the photosensitive layer, anelectrophotographic photoreceptor having high chargeability, sensitivityand responsivity, without deterioration of the electric characteristicsand with scarce injuries of the photosensitive layer even when usedrepetitively can be obtained. Further, stability of the coating solutionupon forming the photosensitive layer by coating can be improved therebycapable of improving the production efficiency of theelectrophotographic photoreceptor.

Upon conducting charging by bringing the charging member into contactwith the obtained electrophotographic photoreceptor, although highelectric field is exerted concentrically to the contacting portion ofthe photosensitive layer and the charging member, since thephotosensitive layer of the electrophotographic photoreceptor has scarceinjuries, charges supplied from the charging member are not concentratedto a portion of the photosensitive layer, and the photosensitive layeris charged uniformly. Namely, the photosensitive layer does not sufferfrom dielectric breakdown by local leakage. Accordingly, the imageforming method of the invention can provide high quality images with noimage defects caused by leakage stably for a long period of time.

Further, according to the invention, since the photosensitive layercontacting the enamine compound represented by the general formula (3)having particularly high charge mobility among the enamine compoundsrepresented by the general formula (2), an electrophotographicphotoreceptor having higher sensitivity and responsivity can beobtained. Accordingly, in the image forming method of the invention,high quality images can be provided even when images are formed at highspeed.

Further, according to the invention, since the ratio A/B for the weightA of the enamine compound represented by the general formula (2) and theweight B of the binder resin in the photosensitive layer is 10/12 to10/30, and since the binder resin is contained at a high ratio in thephotoreceptor, an electrophotographic photoreceptor having a toughphotosensitive layer and excellent in durability can be obtained. As aresult of determining the ratio A/B to 10/12 to 10/30, and increasingthe ratio of the binder resin, the ratio of the enamine compoundrepresented by the general formula (2) is lowered. However, since theenamine compound represented by the general formula (2) has high chargemobility, the electrophotographic photoreceptor has sufficiently highsensitivity and responsivity. Namely, since the electrophotographicphotoreceptor has high sensitivity and responsivity, and is excellent indurability, high quality images can be provided for a long period oftime.

Further, according to the invention, the image forming apparatuscomprises an electrophotographic photoreceptor having a photosensitivelayer containing the enamine compound represented by the general formula(2) and the binder resin, contact charging means for conducting chargingby bringing the charging member into contact with theelectrophotographic photosensitive layer, imagewise exposure means, anddeveloping means. By using the contact charging means, an image formingapparatus with less generation of ozone and usable for a long period oftime can be attained. Further, since the enamine compound represented bythe general formula (2) contained in the photosensitive layer of theelectrophotographic photoreceptor is a charge transportation substancehaving high charge mobility, the electrophotographic photoreceptorequipped to the image forming apparatus has high chargeability,sensitivity and responsivity, with no deterioration of the electriccharacteristics even when used repetitively. Further, since the enaminecompound represented by the general formula (2) is excellent in thecompatibility with the binder resin and in the solubility to thesolvent, it is dispersed uniformly in the binder resin withoutagglomeration, and upon forming the photosensitive layer by coating, itis dissolved uniformly in the coating solution without causingaggregation. Accordingly, the electrophotographic photoreceptor equippedto the image forming apparatus of the invention has a uniformphotosensitive layer with scarce defects. Namely, by incorporating theenamine compound represented by the general formula (2) as a chargetransportation substance in the photosensitive layer, anelectrophotographic photoreceptor having higher chargeability,sensitivity and respectively, with no deterioration of the electriccharacteristics even in a case of repetitive use and with scarce defectsof the photosensitive layer can be obtained. Further, stability of thecoating solution upon forming the photosensitive layer by coating can beimproved, thereby capable of improving the production efficiency of theelectrophotographic photoreceptor.

In a case of contacting a charge member by a contact charging means toan electrophotographic photoreceptor to conduct charging, while a highelectric field is concentrated to the contacting portion in thephotosensitive layer and the charging member, since the photosensitivelayer of the electrophotographic photoreceptor provided to the imageforming apparatus of the invention scarcely has defects as describedabove, charges supplied from the charging member are not concentrated toa portion in the photoreceptor but the photoreceptor is chargeduniformly. That is, the photosensitive layer does not undergo insulationbreakdown by local leakage. Accordingly, it is possible to obtain animage forming apparatus of high reliability capable of providing imagesat high quality with no image defects caused by leakage stably for along period of time.

Further, according to the invention, since the electrophotographicphotoreceptor contains, in the photosensitive layer, the enaminecompound represented by the general formula (3) having particularly highcharge mobility among the enamine compounds represented by the generalformula (2), it has further higher sensitivity and responsivity.Accordingly, it is possible to obtain an image forming apparatus of highreliability capable of providing images at high quality even in a caseof forming images at high speed. Further, since the enamine compoundshown by the following general formula (3), among the enamine compoundsrepresented by the general formula (2), can be synthesized relativelyeasily and can be produced at high yield and reduced cost, theelectrophotographic photoreceptor having excellent electriccharacteristics as described above can be manufactured at a reducedmanufacturing cost. Accordingly, the manufacturing cost of the imageforming apparatus can be reduced,

Further, according to the invention, since the ratio A/B for the weightA of the enamine compound represented by the general formula (2) and theweight B of the binder resin in the photosensitive layer is 10/12 to10/30, and since the binder resin is contained at a high ratio in thephotoreceptor, an electrophotographic photoreceptor having a toughphotosensitive layer and excellent in durability can be obtained. As aresult of determining the ratio A/B to 10/12 to 10/30, and increasingthe ratio of the binder resin, the ratio of the enamine compoundrepresented by the general formula (2) is lowered. However, since theenamine compound represented by the general formula (2) has high chargemobility, the electrophotographic photoreceptor has sufficiently highsensitivity and responsivity. Namely, since the electrophotographicphotoreceptor has high sensitivity and responsivity, and is excellent indurability, high quality images can be provided for a long period oftime.

Further, according to the invention, since the charging member has aroller-like shape, the contact portion between the charging member andthe electrophotographic photoreceptor is large. Accordingly, theelectrophotographic photoreceptor can be charged stably.

Further, according to the invention, since the charging member has abrush-like shape, the contact portion between the charging member andthe electrophotographic photoreceptor is small. Accordingly, since themechanical stress from the charging member to the photosensitive layerof the electrophotographic photoreceptor can be decreased, the life ofthe electrophotographic photoreceptor can be extended. Further, it ispossible to decrease the filming caused when the toner remained on thesurface of the electrophotographic photoreceptor is urged to the surfaceby the charging member.

BRIEF DESCRIPTION OF THE DRAWINGS

Other and further objects, features, and advantages of the inventionwill be more explicit from the following detailed description taken withreference to the drawings wherein:

FIG. 1A is a perspective view schematically showing the constitution ofan electrophotographic photoreceptor 1 according to a first embodimentof the invention; and FIG. 1B is a fragmentary cross sectional viewschematically showing the constitution of the electrophotographicphotoreceptor 1;

FIG. 2 is a schematic cross sectional view schematically showing theconstitution of an electrophotographic photoreceptor according to asecond embodiment of the invention;

FIG. 3 is a schematic cross sectional view schematically showing theconstitution of an electrophotographic photoreceptor according to athird embodiment of the invention;

FIG. 4 is a side elevational view for the arrangement schematicallyshowing the constitution of the electrophotographic apparatus 100;

FIG. 5 is ¹H-NMR spectrum for the product of Preparation Example 1-3;

FIG. 6 is a view showing, in an enlarged scale, 6 ppm to 9 ppm of thespectrum shown in FIG. 5;

FIG. 7 is ¹³C-NMR spectrum according to usual measurement for theproduct of Preparation Example 1-3;

FIG. 8 is a view showing in an enlarged scale 6 ppm to 9 ppm of spectrumshown in FIG. 7;

FIG. 9 is ¹³C-NMR spectrum according to DEPT 135 measurement for theproduct of Preparation Example 1-3;

FIG. 10 is a view showing, in an enlarged scale, 110 ppm to 160 ppm ofthe spectrum shown in FIG. 9;

FIG. 11 is ¹H-NMR spectrum for the product of Preparation Example 2;

FIG. 12 is a view showing, in an enlarged scale, 6 ppm to 9 ppm of thespectrum shown in FIG. 11;

FIG. 13 is ¹³C-NMR spectrum according to usual measurement for theproduct of Preparation Example 2;

FIG. 14 is a view showing, in an enlarged scale, 110 ppm to 160 ppm ofspectrum shown in FIG. 13;

FIG. 15 is ¹³C-NMR spectrum according to DEPT 135 measurement for theproducts of Preparation Example 2;

FIG. 16 is a view showing, in an enlarged scale, 110 ppm to 160 ppm ofthe spectrum shown in FIG. 15;

FIG. 17A is a perspective view schematically showing the constitution ofan electrophotographic photoreceptor 201 according to a fifth embodimentof the invention; and FIG. 17B is a fragmentary cross sectional viewschematically showing the constitution of an electrophotographicphotoreceptor 201;

FIG. 18 is a schematic cross sectional view schematically showing theconstitution of an electrophotographic photoreceptor 202 according to asixth embodiment of the invention;

FIG. 19 is a view for side elevation arrangement schematically showingthe constitution of the image forming apparatus 300;

FIG. 20 is a side elevational view for the arrangement schematicallyshowing the constitution of an image forming apparatus 301 accordig toan eighth embodiment of the invention;

FIG. 21A is a perspective view schematically showing the constitution ofa photoreceptor 310; and FIG. 21B is a fragmentary cross sectional viewschematically showing the constitution of the photoreceptor 310; and

FIG. 22 is a fragmentary cross sectional view schematically showinganother constitution of the photoreceptor mounted to the image formingapparatus 301 shown in FIG. 20.

DETAILED DESCRIPTION

Now referring to the drawings, preferred embodiments of the inventionare described below.

FIG. 1A is a perspective view schematically showing the constitution ofan electrophotographic photoreceptor 1 according to a first embodimentof the invention. FIG. 1B is a fragmentary cross sectional viewschematically showing the constitution of the electrophotographicphotoreceptor 1. The electrophotographic photoreceptor 1 (hereinaftersometimes referred to simply as “photoreceptor”) comprises a cylindricalelectroconductive substrate 11 formed of an electroconductive materialand a photosensitive layer 14 disposed to the outer circumferentialsurface of the electroconductive substrate 11. The photosensitive layer14 has a stacked structure in which a charge generation layer 15containing a charge generation substance 12 that generates charges uponabsorption of light and a charge transportation layer 16 containing acharge transportation substance having an ability of accepting andtransferring charges generated from the charge generation substance 12and a binder resin 17 for binding the charge transportation substance 13stacked in this order on the outer circumferential surface of theelectroconductive substrate 11. That is, the electrophotographicphotoreceptor 1 is a stacked type photoreceptor.

As the binder resin 17 contained in the charge transportation layer 16,a polyarylate resin having the structural unit represented by thefollowing general formula (1) is used.

In the general formula (1), X¹ represents a single bond or —CR⁵R⁶—. R⁵and d R⁶ each represents a hydrogen atom, a halogen atom, an alkyl groupwhich may have a substituent or an aryl group which may have asubstituent. Further, R⁵, R⁶ may join to each other to form a ringstructure.

The single bond means that benzene rings on both sides of X¹ are bondeddirectly. In the general formula (1), specific examples in which X¹ isthe single bond include, for example, constituent units represented bythe structural formula (1-20) shown in Table 4 to be described later.

Specific examples of R⁵ and R⁶ include, in addition to a hydrogen atom,a halogen atom such as a fluorine atom and a chlorine atom, an alkylgroup such as methyl, trifluoromethyl, isopropyl and butyl, and arylgroup such as phenyl, tolyl, α-naphthyl and β-naphthyl. Specificexamples of the ring structure which is formed together with a hydrogenatoms to which R⁵ and R⁶ are bonded when R⁵ and R⁶ join to each otherinclude bivalent groups formed by removing two hydrogen atoms bonding toring carbon atoms of a mono-nuclear or poly-nuclear hydrocarbon such ascycloalkylidene, for example, cyclohexylidene and cyclopentylidene,fluoronylidene, and 1,2,3,4-tetrahydro-2-naphthylidene group.

In the general formula (1) R¹, R², R³, and R⁴ each represents a hydrogenatom, a halogen atom, an alkyl group which have a substituent or an arylgroup which may have a substituent. Specific example of R¹, R², R³, andR⁴ include, in addition to the hydrogen atom, a halogen atom such as afluorine atom and a chlorine atom, an alkyl group such as methyl,trifluoromethyl, isopropyl and butyl, and an aryl group such as phenyl,tolyl, α-naphthyl, and β-naphthyl.

In the general formula (1) R⁷, R⁸, R⁹, and R¹⁰ each represents ahydrogen atom, a halogen atom, an alkyl group which have a substituentor an aryl group which may have a substituent. Specific example of R⁷,R⁸, R⁹, and R¹⁰ include, in addition to the hydrogen atom, a halogenatom such as a fluorine atom and a chlorine atom, an alkyl group such asmethyl, trifluoromethyl, isopropyl and butyl, and an aryl group such asphenyl, α-naphthyl, and β-naphthyl.

The polyarylate resin having the structural unit represented by thegeneral formula (1) is excellent in the mechanical strength.

Since the photosensitive layer 14 has the stacked structure formed bystacking the charge generation layer 15 and the charge transportationlayer 16 in this order on the outer circumferential surface of theelectroconductive substrate 11 as described above, in the electrographicprocess, the charge transportation layer 16 is scraped and worn by ancontact member which is used, for example, upon transfer of toner imageson the surface of the photoreceptor obtained by developing electrostaticlatent images to the recording medium, or upon removing toners remainedon the surface of the photoreceptor after transfer.

However, since the charge transportation layer 16 provided to theelectrophotographic photoreceptor 1 in this embodiment contains thepolyarylate resin having the structural unit represented by the generalformula (1) excellent in the mechanical strength, the wear amount of thecharge transportation layer 16 is small. Accordingly, it is possible toobtain an electrophotographic photoreceptor of excellent wear resistanceand with less change of characteristics due to film scraping of thephotosensitive layer 14.

Among the polyarylate resins having the structural unit represented bythe general formula (1), preferred are polyarylate resins having astructural unit in which X¹ represents —CR⁵R⁶—, R¹, R², R³, R⁴, R⁵, andR⁶ each represents a methyl group, and R⁷, R⁸, R⁹, and R¹⁰ eachrepresents a hydrogen atom in the general formula (1). Since thepolyarylate resin is excellent in the solubility to a solvent, thestability of the coating solution can be improved in a case of formingthe charge transportation layer 16 by coating as will be describedlater. Accordingly, the production efficiency of the electrophotographicphotoreceptor can be improved.

Specific examples of the structural unit represented by the generalformula (1) include, for example, structural units represented by thegeneral formulae shown in the following Table 1 to Table 5, but thestructural unit represented by the general formula (1) are notrestricted to them.

TABLE 1 Structural formula (1-1)

Structural formula (1-2)

Structural formula (1-3)

Structural formula (1-4)

Structural formula (1-5)

TABLE 2 Structural formula (1-6) 

Structural formula (1-7) 

Structural formula (1-8) 

Structural formula (1-9) 

Structural formula (1-10)

TABLE 3 Structural formula (1-11)

Structural formula (1-12)

Structural formula (1-13)

Structural formula (1-14)

Structural formula (1-15)

TABLE 4 Structural formula (1-16)

Structural formula (1-17)

Structural formula (1-18)

Structural formula (1-19)

Structural formula (1-20)

TABLE 5 Structural formula (1-21)

Structural formula (1-22)

Structural formula (1-23)

Structural formula (1-24)

For the polyarylate resin having the structural unit represented by thegeneral formula (1), resins having the structural units selected, forexample, from the structural units represented by the structuralformulae shown in Table 1 to Table 5 described above are used each aloneor two or more or in admixture of two or more of them.

Further, the polyarylate resin having the structural unit represented bythe general formula (1) may have either one or two more of structuralunits represented by the general formula (1). Further, it may have astructural unit other than the structural unit represented by thegeneral formula (1) to such an extent as not deteriorating themechanical strength.

The polyarylate resins having the structural unit represented by thegeneral formula (1) can be manufactured by the known method. Forexample, they can be manufactured by stirring a phthalic acid chlorideand various kinds of bisphenols in a mixed solvent of water and anorganic solvent under the presence of an alkali thereby conductinginterfacial polymerization.

The phthalic acid chloride is usually used as a mixture of terephthalicacid chloride and isophthalic acid chloride for controlling thesolubility with the obtained polyarylate resin. Accordingly, thestructural unit represented by the general formula (1) is expressed as aform to be produced from a mixture of terephthalic acid chloride andisophthalic acid chloride.

The mixing ratio between the terephthalic acid chloride and theisophthalic acid chloride is determined considering the solubility ofthe obtained polyarylate resin. However, since the solubility of theobtained polyarylate resin may sometimes be lowered extremely when anyone of the chlorides is 30 mol % or less of the entire amount of thephthalic acid chloride, the mixing ration between the terephthalic acidchloride and the isophthalic acid chloride is preferably 1:1 by molarratio.

The polyarylate resin having the structural unit represented by thegeneral formula (1) has a viscosity average molecular weight,preferably, of 10,000 or more and 300,000 or less and, more preferably,15,000 or more and 100,000 or less. In a case where the viscosityaverage molecular weight of the polyarylate resin having the structuralunit represented by the general formula (1) is less than 10,000, thecoating film becomes brittle tending to cause injuries to the surface ofthe photosensitive layer 14. In a case where the viscosity averagemolecular weight of the polyarylate resin having the structural unitrepresented by the general formula (1) exceeds 300,000, since theviscosity of the coating solution increases in a case of forming thecharge transportation layer 16 by coating, no uniform coating can beattained to increase the unevenness of the film thickness. According, itis defined as 10,000 or more and 300,000 or less.

The polyarylate resin having the structural unit represented by thegeneral formula (1) may be used in admixture with other binder resinwithin a range not deteriorating the mechanical strength. Other binderresin is selected from those excellent in the compatibility with thepolyarylate resin having the structural unit represented by the generalformula (1). Specific examples include, for example, vinyl polymerresins such as polymethyl methacrylate resin, polystyrene resin, andpolyvinyl chloride resin, and copolymer resins thereof, as well as thoseresins having the structural units other than the structural unitrepresented by the general formula (1) such as polyarylate resin,polycarbonate resin, polyester resin, polyester carbonate resin,polysulfone resin, phenoxy resin, epoxy resin, silicone resin, polyamideresin, polyether resin, polyurethane resin, polyacrylamide resin, andphenol resin. Further, thermosetting resins obtained by partiallycrosslinking the resins described above may also be used.

The charge transportation layer 16 is formed by binding the chargetransportation substance 13 to the binder resin 17 containing thepolyarylate resin having the structural unit represented by the generalformula (1). As the charge transportation substance 13, an enaminecompound represented by the following general formula (2) is used.

[Ka 11]

In the general formula (2), Ar¹ and Ar² each represents an aryl groupwhich may have a substituent or a heterocyclic group which may have asubstituent. Ar³ represents an aryl group which may have a substituent,a heterocyclic group which may have a substituent, an aralkyl groupwhich may have a substituent, or an alkyl group which may have asubstituent. Ar⁴ and Ar⁵ each represents a hydrogen atom, an aryl groupwhich may have a substituent, a heterocyclic group which may have asubstituent, an aralkyl group which may have a substituent, or an alkylgroup which may have a substituent. However, both Ar⁴ and Ar⁵ do notform the hydrogen atoms. Ar⁴ and Ar⁵ may join to each other by way of anatom or an atomic group to form a ring structure. “a” represents analkyl group which may have a substituent, an alkoxy group which may havea substituent, a dialkylamino group which may have a substituent, anaryl group which may have a substituent, a halogen atom or a hydrogenatom, and m represents an integer of 1 to 6. In a case where m is 2 ormore, plural a may be identical or different with each other or may jointo each other to form a ring structure. R¹¹ represents a hydrogen atom,a halogen atom, or an alkyl group which may have a substituent. R¹²,R¹³, and R¹⁴ each represents a hydrogen atom, an alkyl group which mayhave a substituent, an aryl group which may have a substituent, aheterocyclic group which may have a substituent, or an aralkyl groupwhich may have a substituent. n represents an integer of 0 to 3 and in acase where n is 2 or 3, plural R¹² may be identical or different witheach other, and plural R¹³ may be identical or different with eachother. However, in a case where n represents 0, Ar³ represents aheterocyclic ring which may have a substituent.

In the general formula (2), specific examples of the aryl grouprepresented by Ar¹, Ar², Ar³, Ar⁴, Ar⁵, a, R¹², R¹³ or R¹⁴ include, forexample, phenyl, naphthyl, pyrenyl and anthryl. The substituent whichmay be present on the aryl group include, for example, an alkyl groupsuch as methyl, ethyl, propyl, and trifluoromethyl, an alkeny group suchas 2-propenyl and styryl, an alkoxy group such as methoxy, ethoxy andpropoxy, an amino group such as methylamino and dimethylamino, a halogengroup such as fluoro, chloro and bromo, an aryl group such as phenyl andnaphthyl, an aryloxy group such as phenoxy, and an arylthio group suchas thiophenoxy. Specific examples of the aryl group having suchsubstituent include, for example, tolyl, methoxyphenyl, biphenylyl,terphenyl, phenoxyphenyl, p-(phenylthio)phenyl and p-stylylphenyl.

Specific examples of the heterocyclic group represented by Ar¹, Ar²,Ar³, Ar⁴, Ar⁵, R¹², R¹³, or R¹⁴ in the general formula (2) include, forexample, furyl, thienyl, thiazolyl, benzofuryl, benzothiophenyl,benzothiazolyl, and benzooxazolyl. The substituent which may be presenton the heterocyclic group described above include those substituentidentical with the substituents that may be present on the aryl groupshown, for example, by Ar¹, and specific examples of the heterocyclicgroup which may have a substituent include, for example,N-methylindolyl, and N-methylcarbazolyl.

Specific examples of the aralkyl group represented by Ar³, Ar⁴, Ar⁵,R¹², R¹³, or R¹⁴ in the general formula (2) include, for example, benzyland 1-naphthylmethyl. The substituent which may be present on thearalkyl group described above include, those substituents identical withthe substituent which may be present on the aryl group shown, forexample, by Ar¹, and specific examples of the aralkyl group having thesubstituent include, for example, p-methoxybenzyl.

As the alkyl group represented by Ar³, Ar⁴, Ar⁵, a, R¹¹, R¹², R¹³, orR¹⁴ in the general formula (2), those of 1 to 6 carbon atoms arepreferred, and specific examples include, for example, a chained alkylgroup such as methyl, ethyl, n-propyl, isopropyl, and t-butyl, as wellas a cycloalkyl group such as cyclohexyl and cyclopentyl. Thesubstituent that may be present on the alkyl groups described aboveinclude those substituents identical with the substituents that may bepresent on the aryl group represented, for example, by Ar¹ describedabove. Specific examples of the alkyl group having the substituentinclude, for example, a halogenated alkyl group such as trifuloromethyland fluoromethyl, an alkoxyalkyl group such as 1-methoxyethyl and analkyl group substituted with a heterocyclic group such as2-thienylmethyl.

As the alkoxy group represented by a in the general formula (2), thoseof 1 to 4 carbon atoms are preferred and specific examples include, forexample, methoxy, ethoxy, n-propoxy, and isopropoxy. The substituentsthat may be present on the alkoxy group include those substituentsidentical with the substituents that may be present on the aryl grouprepresented, for example, by Ar¹ described above.

As the dialkylamino group represented by a in the general formula (2),those substituted with an alkyl group of 1 to 4 carbon atoms arepreferred and specific examples include, for example, dimethylamino,diethylamino, and diisopropylamino. The substituent that may be presenton the dialkylamino groups include those substituents identical with thesubstituents that may be present on the aryl group shown, for example,by Ar¹ described above.

Specific examples of the halogen atom represented by a or R¹¹ in thegeneral formula (2) include, for example, a fluorine atoms and achlorine atoms.

Specific examples of the atom for bonding with Ar⁴ and Ar⁵ in thegeneral formula (2) include, for example, an oxygen atom, a sulfur atomand a nitrogen atom. The nitrogen atom can bond in the form of abivalent group such as an imino group or N-alkylimino group with Ar⁴ andAr⁵. Specific examples of the atomic group for bonding with Ar⁴ and Ar⁵include, for example, those bivalent groups, for example, an alkylenegroup such as methylene, ethylene and methylmethylene, an alkenylenegroup such as vinylene and propenylene, an alkylene group containing ahetero atom such as oxymethylene (chemical formula: —O—CH₂—), as well asan alkenylene group containing a hetero atom such as thiovinylene(chemical formula: -s-CH═CH—).

Since the enamine compound represented by the general formula (2) isexcellent in the compatibility with the polyarylate resin having thestructural unit represented by the general formula (1) and has highcharge mobility, it is possible to obtain an electrophotographicphotoreceptor having high charge potential, high sensitivity, showingsufficient responsivity and not suffering from deterioration of theelectric characteristics even during repetitive use also in a case wherethe charge transportation layer 16 contains a polyarylate resin havingthe structural unit represented by the general formula (1).

Accordingly, when the polyarylate resin having the structural unitrepresented by the general formula (1) and the enamine compoundrepresented by the general formula (2) are incorporated in combinationin the charge transportation layer 16, it is possible to obtain anelectrophotographic photoreceptor of high durability that is excellentin the mechanical strength and capable of enduring increase in themechanical stress accompanied by digitalization and increased resolutionin the electrophotographic apparatus, as well as capable of providingfavorable electric characteristics stably over a long period of time.

In the general formula (3), b, c and d each represent anoptionally-substituted alkyl group, an optionally-substituted alkoxygroup, an optionally-substituted dialkylamino group, anoptionally-substituted aryl group, a halogen atom, or a hydrogen atom;i, k and j each indicate an integer of from 1 to 5; when i is 2 or more,then the “b”s may be the same or different and may bond to each other toform a cyclic structure; when k is 2 or more, then the “c”s may be thesame or different and may bond to each other to form a cyclic structure;and when j is 2 or more, then the “d”s may be the same or different andmay bond to each other to form a cyclic structure; Ar⁴, Ar⁵ “a” and “m”represent the same as those defined in formula (1).

In the general formula (3), as the alkyl group represented by b, c, andd, those of 1 to 6 carbon atoms are preferred and specific examplesinclude, for example, a chained alkyl group such as methyl, ethyl,n-propyl, and isopropyl, and a cloalkyl group such as cyclohexyl andcyclopentyl. The substituents that can be present on the alkyl groupinclude those substituents identical with the substituents that may bepresent on the aryl group shown, for example, by Ar¹ described above andspecific examples of the alkyl group having the substituent include, forexample, a halogenated alkyl group such as trifluoromethyl andfluoromethyl, an alkoxyalkyl group such as 1-methoxyethyl, and an alkylgroup substituted with a heterocyclic group such as 2-thienylmethyl.

As the alkoxy group represented by b, c, and d in the general formula(3), those of 1 to 4 carbon atoms are preferred and specific examplesinclude, for example, methoxy, ethoxy, n-propoxy and isopropoxy. Thesubstituents that may be present on the alkoxy groups include thosesubstituents identical with the substituents which may be present on thearyl group shown, for example, by Ar¹.

As the dialkylamino group represented by b, c, or d in the generalformula (3), those substituted with an alkyl group of 1 to 4 carbonatoms are preferred and specific examples include, for example,dimethylamino, diethylamino, and diisopropyl amino. The substituentsthat may be present on the dialkylamino group include those substituentsidentical with the substituents that may be present on the aryl group,for example, shown by Ar¹.

Specific examples of the aryl group represented by b, c, or d in thegeneral formula (3) include, for example, phenyl and naphthyl. Thesubstituents which may be present on the aryl groups include, thosesubstituents identical with the substituents which may be present on thearyl group, for example, shown by Ar¹, and specific examples of the arylgroup having the substituent include, for example, tolyl andmethoxyphenyl.

Specific examples of the halogen atom represented by b, c, or d in thegeneral formula (3) include, for example, fluorine atom and chlorineatom.

The enamine compound represented by the general formula (3) hasparticularly high charge mobility. Accordingly, by incorporating theenamine compound represented by the general formula (3) into thephotosensitive layer 14, it is possible to obtain an electrophotographicphotoreceptor of high reliability showing high charge potential, highsensitivity, and sufficient responsivity, and excellent in thedurability with no deterioration of the characteristics even in a caseof use in the high speed electrophotographic process.

Further, among the enamine compounds represented by the general formula(2), compounds particularly excellent in view of the characteristics,the cost, the productivity, etc. include those in which Ar¹ and Ar² eachrepresents a phenyl group, Ar³ represents a phenyl group, tolyl group,p-methoxyphenyl group, biphenylyl group, naphthyl group or thienylgroup, at least one of Ar⁴ and Ar⁵ represents a phenyl group, p-tolylgroup, p-methyxyphenyl group, naphthyl group, thienyl group, orthiazolyl group, each of R¹¹, R¹², R¹³, and R¹⁴ is a hydrogen atom, andn is 1.

Specific examples of the enamine compound represented by the generalformula (2) include, for example, those exemplified compounds having thegroups shown in the following Table 6 to Table 37 but the enaminecompounds represented by the general formula (2) are not restricted tothem. Each of the groups shown in Table 6 to Table 37 corresponds toeach of the groups in the general formula (2). For example, theExemplified Compound No. 1 shown in Table 6 is an enamine compound shownby the following structural formula (2-1).

[Ka 13]

In a case where Ar⁴ and Ar⁵ join to each other by way of an atom or anatomic group to form a ring structure, the carbon-carbon double bond towhich Ar⁴ and Ar⁵ are bonded, and a ring structure formed with Ar⁴ andAr⁵ together with the carbon atoms of the carbon-carbon double bond areshown together from the column for Ar⁴ to the column Ar⁵ in Table 6 toTable 37.

TABLE 6       Compound No.         Ar¹         Ar²         R¹¹        Ar³

1

H

2

H

3

H

4

H

5

H

6

H

7

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 1 1 CH═CH H H

2 1 CH═CH H H

3 1 CH═CH H —CH₃

4 1 CH═CH H H

5 1 CH═CH H H

6 1 CH═CH H H

7 1 CH═CH H —CH₃

TABLE 7       Compound No.         Ar¹         Ar²         R¹¹        Ar³

 8

H

 9

H

10

H

11

H

12

H

13

H

14

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵  8 1 CH═CH H H

 9 1 CH═CH H —CH₃

10 1 CH═CH H —CH₃

11 1 CH═CH H H

12 1 CH═CH H H

13 1 CH═CH H H

14 1 CH═CH H H

TABLE 8       Compound No.         Ar¹         Ar²         R¹¹        Ar³

15

H

16

H

17

H

18

H

19

H

20

H

21

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 15 1 CH═CH H H

16 1 CH═CH H —CH₃

17 1 CH═CH H H

18 1 CH═CH H —CH₃

19 1 CH═CH H H

20 1 CH═CH H H

21 1 CH═CH H H

TABLE 9       Compound No.         Ar¹         Ar²         R¹¹        Ar³

22

H

23

H

24

H

25

H

26

H

27

H

28

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 22 1 CH═CH H H

23 1 CH═CH H —CH₃

24 1 CH═CH H —CH₃

25 1 CH═CH H H

26 1 CH═CH H H

27 1 CH═CH H H

28 1 CH═CH H

TABLE 10       Compound No.         Ar¹         Ar²         R¹¹        Ar³

29

H

30

H

31

H

32

H

33

H

34

H

35

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 29 1 CH═CH H

30 1 CH═CH H

31 1 CH═CH H

32 1 CH═CH H

33 1 CH═CH H

34 1 CH═CH H

35 1 CH═CH H

TABLE 11       Compound No.         Ar¹         Ar²         R¹¹        Ar³

36

H

37

H

38

H

39

H

40

H

41

H

42

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 36 1 CH═CH H

37 1 CH═CH H

38 1 CH═CH H

39 1 CH═CH —CH₃ H

40 1 CH═CH

H

41 1

H H

42 1

H H

TABLE 12       Compound No.         Ar¹         Ar²         R¹¹        Ar³

43

H

44

H

45

H

46

H

47

H

48

H

49

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 43 1

H H

44 1

H H

45 1

H

46 2 CH═CH—CH═CH H H

47 2 CH═CH—CH═CH H H

48 2 CH═CH—CH═CH H —CH₃

49 2 CH═CH—CH═CH H —CH₃

TABLE 13       Compound No.         Ar¹         Ar²         R¹¹        Ar³

50

H

51

H

52

H

53

H

54

H

55

H

56

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 50 2 CH═CH—CH═CH H —CH₃

51 2 CH═CH—CH═CH H —CH₃

52 2

H H

53 2

H H

54 3

H H

55 1 CH═CH H H

56 1 CH═CH H H

TABLE 14       Compound No.         Ar¹         Ar²         R¹¹        Ar³

57

H

58

H

59

H

60

H

61

H

62

H

63

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 57 1 CH═CH H H

58 1 CH═CH H H

59 1 CH═CH H H

60 1 CH═CH H H

61 1 CH═CH H H

62 1 CH═CH H H

63 1 CH═CH H —CH₃

TABLE 15       Compound No.         Ar¹         Ar²         R¹¹        Ar³

64

H

65

H

66

H

67

H

68

H

69

H

70

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 64 1 CH═CH H H

65 1 CH═CH H H

66 1 CH═CH H —CH₃

67 1 CH═CH H H

68 1 CH═CH H H

69 1 CH═CH H H

70 1 CH═CH H H

TABLE 16       Compound No.         Ar¹         Ar²         R¹¹        Ar³

71

H

72

H

73

H

74

H

75

H

76

H

77

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 71 1 CH═CH H H

72 1 CH═CH H H

73 1 CH═CH H H

74 1 CH═CH H H

75 1 CH═CH H H

76 1 CH═CH H H

77 1 CH═CH H H

TABLE 17       Compound No.         Ar¹         Ar²         R¹¹        Ar³

78

H

79

H

80

H

81

H

82

H

83

H

84

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 78 1 CH═CH H H

79 1 CH═CH H H

80 1 CH═CH H H

81 1 CH═CH H H

82 1 CH═CH H H

83 1 CH═CH H H

84 1 CH═CH H H

TABLE 18       Compound No.         Ar¹         Ar²         R¹¹        Ar³

85

H

86

H

87

H

88

H

89

H

90

H

91

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 85 1 CH═CH H —CH₃

86 1 CH═CH H —CH₃

87 1 CH═CH H —CH₃

88 1 CH═CH H

89 1 CH═CH H

90 1 CH═CH H

91 1 CH═CH H

TABLE 19       Compound No.         Ar¹         Ar²         R¹¹        Ar³

92

H

93

H

94

H

95

H

96

H

97

H

98

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 92 1 CH═CH H

93 1 CH═CH H

94 1 CH═CH H

95 1 CH═CH H

96 1 CH═CH H

97 1 CH═CH H

98 1 CH═CH H

TABLE 20       Compound No.         Ar¹         Ar²         R¹¹        Ar³

 99

H

100

H

101

H

102

H

103

H

104

H

105

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵  99 1 CH═CH —CH₃ H

100 1 CH═CH

H

101 1

H H

102 1

H H

103 1

H H

104 1

H H

105 1

H

TABLE 21       Compound No.         Ar¹         Ar²         R¹¹        Ar³

106

H

107

H

108

H

109

H

110

H

111

H

112

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 106 2 CH═CH—CH═CH H H

107 2 CH═CH—CH═CH H H

108 2 CH═CH—CH═CH H —CH₃

109 2 CH═CH—CH═CH H —CH₃

110 2 CH═CH—CH═CH H —CH₃

111 2 CH═CH—CH═CH H —CH₃

112 2 CH═CH—CH═CH H H

TABLE 22       Compound No.         Ar¹         Ar²         R¹¹        Ar³

113

H

114

H

115

H

116

H

117

H

118

H

119

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 113 2

H H

114 2

H H

115 3

H H

116 1 CH═CH H H

117 1 CH═CH H H

118 1 CH═CH H H

119 1 CH═CH H H

TABLE 23       Compound No.         Ar¹         Ar²         R¹¹        Ar³

120

H

121

H

122

H

123

H

124

H

125

H

126

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 120 1 CH═CH H H

121 1 CH═CH H H

122 1 CH═CH H H

123 1 CH═CH H —CH₃

124 1 CH═CH H

125 1 CH═CH H H

126 1 CH═CH H H

TABLE 24       Compound No.         Ar¹         Ar²         R¹¹        Ar³

127

H

128

H

129

H

130

H

131

H

132

H

133

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 127 1 CH═CH H

128 1 CH═CH H H

129 1 CH═CH H H

130 1 CH═CH H

131 1 CH═CH H H

132 1 CH═CH H —CH₃

133 1 CH═CH H

TABLE 25       Compound No.         Ar¹         Ar²         R¹¹        Ar³

134

H

135

H

136

H

137

H

138

H

139

H

140

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 134 1 CH═CH H H

135 1 CH═CH H H

136 1 CH═CH H

137 1 CH═CH H H

138 1 CH═CH H —CH₃

139 1 CH═CH H

140 1 CH═CH H H

TABLE 26       Compound No.         Ar¹         Ar²         R¹¹        Ar³

141

H

142

H

143

H

144

H

145

H

146

H

147

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 141 1 CH═CH H H

142 1 CH═CH H —CH₃

143 1 CH═CH H H

144 1 CH═CH H —CH₃

145 1 CH═CH H —CH₃

146 1 CH═CH H H

147 1 CH═CH H —CH₃

TABLE 27       Compound No.         Ar¹         Ar²         R¹¹        Ar³

148

H

149

H

150

H

151

H

152

H

153

H

154

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 148 1 CH═CH H H

149 1 CH═CH H —CH₃

150 1 CH═CH H H

151 1 CH═CH H —CH₃

152 1 CH═CH H —CH₃

153 1 CH═CH H —CH₃

154 1 CH═CH H H

TABLE 28       Compound No.         Ar¹         Ar²         R¹¹        Ar³

155

H

156

H

157

H

158

H

159

H

160

H

161

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 155 1 CH═CH H —CH₃

156 1 CH═CH H —CH₃

157 1 CH═CH H —CH₃

158 1 CH═CH H H

159 1 CH═CH H

160 1 CH═CH H

161 1 CH═CH H

TABLE 29       Compound No.         Ar¹         Ar²         R¹¹        Ar³

162

H

163

H

164

H

165

H

166

H

167

H

168

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 162 1 CH═CH H

163 1 CH═CH H

164 1 CH═CH H

165 2 CH═CH—CH═CH H H

166 2 CH═CH—CH═CH H —CH₃

167 2 CH═CH—CH═CH H —CH₃

168 3

H H

TABLE 30       Compound No.         Ar¹         Ar²         R¹¹        Ar³

169

H

170

H

171

H

172

H

173

H

174

H

175

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 169 1 CH═CH H H

170 1 CH═CH H H

171 1 CH═CH H H

172 1 CH═CH H H

173 1 CH═CH H H

174 1 CH═CH H H

175 1 CH═CH H H

TABLE 31       Compound No.         Ar¹         Ar²         R¹¹        Ar³

176

H

177

H

178

H

179

H

180

H

181

H

182

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 176 1 CH═CH H H

177 1 CH═CH H H

178 1 CH═CH H

179 1 CH═CH H H

180 1 CH═CH H —CH₃

181 1 CH═CH H

182 1 CH═CH H H

TABLE 32       Compound No.         Ar¹         Ar²         R¹¹        Ar³

183

H

184

H

185

H

186

H

187

H

188

H

189

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 183 1 CH═CH H —CH₃

184 1 CH═CH H

185 1 CH═CH H H

186 1 CH═CH H H

187 1 CH═CH H

188 0 — H H

189 0 — H H

TABLE 33       Compound No.         Ar¹         Ar²         R¹¹        Ar³

190

H

191

H

192

H

193

H

194

H

195

H

196

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 190 0 — H H

191 0 — H H

192 0 — H H

193 0 — H H

194 0 — H

195 0 — H H

196 0 — H H

TABLE 34       Compound No.         Ar¹         Ar²         R¹¹        Ar³

197

H

198

H

199

H

200

H

201

H

202

H

203

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 197 0 — H H

198 0 — H H

199 0 — H H

200 0 — H H

201 0 — H

202 0 — H H

203 0 — H H

TABLE 35       Compound No.         Ar¹         Ar²         R¹¹        Ar³

204

H

205

H

206

H

207

H

208

H

209

CH₃

210

CH₂CF₃

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 204 0 — H H

205 0 — H

206 0 — H H

207 0 — H H

208 0 — H

209 1 CH═CH H H

210 1 CH═CH H H

TABLE 36 Compound No. Ar¹ Ar² R¹¹ Ar³ 211

CH(CH₃)₂

212

F

213

H

214

H

215

H

216

H

217

H

        Compound No.

          n          

          R¹⁴           Ar⁴           Ar⁵ 211

1 CH═CH H H

212

1 CH═CH H H

213

1 CH═CH H H

214

1 CH═CH H H

215

1 CH═CH H H

216

1 CH═CH H H

217

1 CH═CH H H

TABLE 37       Compound No.         Ar¹         Ar²         R¹¹        Ar³

218

H

219

H

220

H

Compound No.   n  

  R¹⁴   Ar⁴   Ar⁵ 218 1 CH═CH H H

219 1 CH═CH H H

220 1 CH═CH H H

For the enamine compound represented by the general formula (2), thecompounds selected from the group consisting, for example, ofexemplified compounds shown in Table 6 to Table 37 described above areused each alone or in admixture of two or more of them.

The enamine compound represented by the general formula (2) can beproduced, for example, as described below.

At first, an aldehyde compound or a ketone compound represented by thefollowing general formula (4) and a secondary amine compound representedby the following general formula (5) are put to dehydrating condensationreaction to prepare an enamine intermediate represented by the followinggeneral formula (6):

(in which Ar¹, Ar², and R¹¹ have the same meanings as defined for thegeneral formula (2)),[Ka 15]

(in which Ar³, a, and m have the same meanings as defined for thegeneral formula (2)),

(in which Ar¹, Ar², Ar³, R¹¹, a and m have the same meanings as definedfor the general formula (2)).

The dehydrating condensation reaction is conducted, for example, asdescribed below. The aldehyde compound or ketone compound represented bythe general formula (4) and the secondary amine compound represented bythe general formula (5) in a substantially equi-molar amount therewithare dissolved in a solvent such as an aromatic solvent, alcohols orethers to prepare a solution. Specific examples of the solvent to beused include, for example, toluene, xylene, chlorobenzene, butanol anddiethylene glycol dimethyl ether. A catalyst such as an acid catalyst,for example, p-toluene sulfonic acid, camphor sulfonic acid, orpyridinium-p-toluene sulfonic acid is added to the thus preparedsolution and they are reacted under heating. The addition amount of thecatalyst to the aldehyde compound or the ketone compound represented bythe general formula (4) is, preferably, 1/10 to 1/1000 molar amount and,more preferably, from 1/25 to 1/500 molar amount, with 1/50 to 1/200molar amount being optimal. Since water is by-produced during reactionto hinder the reaction, formed water is put to azeotropic boilingtogether with the solvent and removed out of the system. This canproduce the enamine intermediate product represented by the generalformula (6) at a high yield.

Then, the enamine intermediate product represented by the generalformula (6) is formulated by the Vilsmeier reaction, or acylated by theFriedel-Craft reaction to produce an enamine-carbonyl intermediaterepresented by the following general formula (7). In this case, whenformulation by the Vilsmeier reaction is taken place, anenamine-aldehyde intermediate product represented by the followinggeneral formula (7) in which R¹⁵ is a hydrogen atom can be prepared asthe enamine-carbonyl intermediate product. In this case, when acylationby the Friedel-craft reaction is taken place, an enamine-ketointermediate product represented by the following general formula (7) inwhich R¹⁵ is a group other than the hydrogen atom can be produced as theenamine-carbonyl intermediate product.

(in which R¹⁵ represents R¹⁴ when n is 0 and represents R¹² when n is 1,2, or 3 in the general formula (2), and Ar¹, Ar², Ar³ R¹¹, R¹², R¹⁴, a,m, and n have the same meanings as defined for the general formula (2)).

The Vilsmeier reaction is taken place, for example, as described below.Phosphorus oxychloride and N,N-dimethylformamide, phosphorus oxychlorideand N-methyl-N-phenylformamide, or phosphorus oxychloride andN,N-dimethylformamide were added in a solvent such asN,N-dimetylformamide (simply referred to as DMF) or 1,2-dichloroethane,to prepare a Vilsmeier reagent. 1.0 equivalent amount of the enamineintermediate product represented by the general formula (6) is added to1.0 to 1.3 equivalent amount of the prepared Vilsmeier reagent andstirred under heating at 60 to 110° C. for 2 to 8 hours. Then,hydrolysis is conducted in a 1N to 8N aqueous solution of sodiumhydroxide or an aqueous solution of potassium hydroxide. Thus, anenamine aldehyde intermediate product in which R¹⁵ is a hydrogen atom inthe enamine-carbonyl intermediate product represented by the generalformula (7) can be prepared at a high yield.

Further, the Friedel-Craft reaction is taken place, for example, asdescribed below. 1.0 to 1.3 equivalent amount of the reagent preparedfrom aluminum chloride and acid chloride, and 1.0 equivalent amount ofthe enamine intermediate product represented by the general formula (6)are added in a solvent such as 1,2-dichloroethane and stirred at −40 to80° C. for 2 to 8 hours. Heating is applied depending on the case. Then,hydrolysis is conducted in a 1N to 8N aqueous solution of sodiumhydroxide or aqueous solution of potassium hydroxide. Thus, anenamine-keto intermediate product represented by the general formula (7)in which R¹⁵ is a group other than the hydrogen atom in theenamine-carbonyl intermediate product can be produced at a high yield.

Finally, by conducting Wittig-Horner reaction of reacting theenamine-carbonyl intermediate product represented by the general formula(7) and the Wittig reagent represented by the following general formula(8-1) or (8-2) under the basic condition, the enamine compoundrepresented by the general formula (2) can be produced. In this case,when the Wittig reagent represented by the general formula (8-1) isused, the enamine compound represented by the general formula (2) inwhich n=0 can be obtained and, in a case of using the Wittig reagentrepresented by the general formula (8-2) is used, an enamine compoundrepresented by the general formula (2) in which n is 1, 2 or 3 can beobtained.

(in which R¹⁶ represents an alkyl group which may have a substituent oran aryl group which may have a substituent, and Ar⁴ and Ar⁵ have thesame meanings as those defined for the general formula (2))

(in which R¹⁶ represents an alkyl group which may have a substituent oran aryl group which may have a substituent, n represents an integer of 1to 3, and Ar⁴, Ar⁵, R¹², R¹³ and R¹⁴ have the same meanings as thosedefined for the general formula (2)).

The Wittig-Horner reaction is conducted, for example, as describedbelow. 1.0 equivalent amount of the enamine-carbonyl intermediateproduct represented by the general formula (7), 1.0 to 1.20 equivalentamount of the Wittig reagent represented by the general formula (8-1) or(8-2), and 1.0 to 1.5 equivalent amount of a metal alkoxide base such aspotassium t-butoxide, sodium ethoxide, or sodium methoxide are added ina solvent, for example, toluene, xylene, diethylether, tetrahydrofuran(simply referred to as THF), ethylene glycol dimethyl ether,N,N-dimethylformamide, or dimethyl sulfoxide and stirred at a roomtemperature or under heating at 30 to 60° C., for 2 to 8 hours. Thus,the enamine compound represented by the general formula (2) can beproduced at a high yield.

The enamine compound represented by the general formula (2) may be usedin admixture with other charge transportation substances. The othercharge transportation substances which are used in admixture with theenamine compound represented by the general formula (2) include, forexample, carbazole derivatives, oxyzole derivatives, oxadiazolederivatives, thiazole derivatives, thiadiazole derivatives, triazolederivatives, imidazole derivatives, imidazolone derivatives,imidazolidine derivatives, bisimidazolidine derivatives, stylylcompounds, hydrozone compounds, polynuclear aromatic compounds, indolederivatives, pyrazoline derivatives, oxazolone derivatives,benzimidazole derivatives, quinazoline derivatives, benzofuranderivatives, acridine derivatives, phenadine derivatives, aminostilbenederivatives, triarylamine derivatives, triarylmethane derivatives,phenylenediamine derivatives, stilbene derivatives, and benzidinederivatives. Further, polymers having the groups derived from thecompounds in the main chain or the side chain, for example,poly-N-vinylcarbazole, poly-1-vinylpyrene, and poly-9-vinylanthracenecan also be mentioned.

However, for attaining particularly high charge transportation ability,it is preferred that the entire amount of the charge transportationsubstance 13 comprises the enamine compound represented by the generalformula (2).

The ration (A/B) between the charge transportation substance 13 (A) andthe binder resin 17 (B) in the charge transportation layer is preferably10/12 or less by weight ratio. This can improve the wear resistance ofthe photosensitive layer 14.

Further, the ratio A/B is preferably 10/30 or more by weight ratio in acase of forming the charge transportation layer 16 by a dip coatingmethod to be described later. In a case where the ratio A/B is less than10/30 and the ratio of the binder resin 17 is excessively high, sincethe viscosity of the coating solution increases, it results in loweringof the coating speed to remarkably worsen the productivity. Further, ina case of increasing the amount of the solvent in the coating solutionin order to suppress the increase of the viscosity of the coatingsolution, a brushing phenomenon occurs to cause clouding in the formedcharge transportation layer 16.

An additive such as a plasticizer or a leveling agent may also be addedto the charge transportation layer 16 optionally in order to improve thefilm forming property, flexibility and surface smoothness. Theplasticizer include, for example, a dibasic acid ester such as phthalateester, fatty acid ester, phosphorate ester, chlorinated paraffin, andepoxy plasticizer. The leveling agent include, for example, siliconetype leveling agent.

Fine particles of an inorganic compound or an organic compound may beadded to the charge transportation layer 16 in order to increase themechanical strength or improve the electric characteristics.

Further, various additives such as an antioxidant and a sensitizer maybe added optionally to the charge transportation layer 16. This canimprove potential characteristics. Further, the stability of the coatingsolution upon forming the charge transportation layer 16 by coating isimproved as will be described later. Further, this can mitigate thefatigue deterioration to improve the durability upon repetitive use ofthe photoreceptor.

As the antioxidant, hindered phenol derivatives or hindered aminederivatives are used preferably. The hindered phenol derivatives arepreferably used within a range of 0.1% by weight or more and 50% byweight or less relative to the charge transportation substance 13.Further, the hindered amine derivatives are used preferably within arange from 0.1% by weight or more and 50% by weight or less relative tothe charge transportation substance 13. The hindered phenol derivativeand the hindered amine derivative may be used in admixture. In thiscase, the total amount of the hindered phenol derivative and thehindered amine derivative to be used is preferably within a range from0.1% by weight or more and 50% by weight or less relative to the chargetransportation substance 13. In a case where the amount of the hinderedphenol derivative to be used, the amount of the hindered aminederivative to be used, or the total amount of the hindered phenolderivative and the hindered amine derivative to be used is less than0.1% by weight, no sufficient effect can be obtained for the improvementof the stability of the coating solution and the improvement of thedurability of the photoreceptor. Further, if the amount exceeds 50% byweight, this gives an undesired effect on the characteristics of thephotoreceptor. Accordingly, it is defined as 0.1% by weight or more and50% by weight or less.

The charge transportation layer 16 is formed, for example, by dissolvingor dispersing, in an appropriate solvent, the charge transportationsubstance 13 containing the enamine compound represented by the generalformula (2) described above and the binder resin 17 containing thepolyarylate resin having the structural unit represented by the generalformula (1), and the additives described above, if necessary, to preparea coating solution for a charge transportation layer, and coating theobtained solution on the outer circumferential surface of the chargegeneration layer 15.

The solvent for the coating solution for the charge transportation layercan include, for example, aromatic hydrocarbons such as benzene,toluene, xylene and monochlorobenzene, halogenated hydrocarbon such asdichloromethane and dichloroethane, ethers such as tetrahydfofuran,dioxane and dimethoxymethyl ether, as well as aprotic polar solventssuch as N,N-dimethylformamide. The solvents may be used each alone ortwo or more of them may be used in admixture. Further, the solventsdescribed above may also be used with a further addition of alcohols oracetonitrile or methyl ethyl ketone optionally.

The coating method for the coating solution for charge transportationlayer includes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method or dip coating method.Among the coating methods described above, an optimal method can beselected while taking the physical properties of the coating and theproductivity into consideration. Among the coating methods describedabove, since the dip coating method is a method of dipping a substrateinto a coating bath filled with the coating solution and then pulling upthe substrate at a constant speed or at a gradually changing speed toform a layer on the surface of the substrate and, since the method isrelatively simple and excellent in view of the productivity and thecost, it has been often utilized in a case of producing anelectrophotographic photoreceptor and also often utilized in a case offorming the charge transportation layer 16.

The film thickness of the charge transportation layer 16 is preferably,5 μm or more and 50 μm or less and, more preferably, 10 μm or more and40 μm or less. In a case where the film thickness of the chargetransportation layer 16 is less than 5 μm, the charge retainability onthe surface of the photoreceptor is lowered. In a case where the filmthickness of the charge transportation layer 16 exceeds 50 μm,resolution of the photoreceptor is lowered. Accordingly, it is definedas 5 μm or more and 50 μm or less.

As described above, the photosensitive layer 14 has a stacked structureof the charge generation layer 15 containing the charge generationsubstance 12 and the charge transportation layer 16 containing thecharge transportation substance 13. By sharing the charge generatingfunction and the charge transporting function respectively to separatelayers, since optimal materials can be selected for the chargegenerating function and the charge transporting function respectively, aphotoreceptor having higher sensitivity and of high durability furtherimproved stability upon repetitive use can be obtained.

The charge generation layer 15 contains the charge generation substance12 as a main ingredient. The material effective as the charge generationsubstance 12 includes azo pigments such as a monoazo pigment, bisazopigment, and trisazo pigment, indigo pigments such as indigo andthioindigo, perylene pigments such as peryleneimide and perylenic acidanhydride, polynuclear quinone pigments such as anthraquinone andpyrenequinone, phthalocyanine pigments such as metal phthalocyanine andnon-metal phthalocyanine, squarylium dyes, pyrylium salts andthiopyrylium salts, triphenylmethane dyes, and inorganic materials suchas selenium and amorphous silicon. The charge generation substances areused each alone or two or more of them in combination.

Among the charge generation substances described above, use ofoxotitanium phthalocyanine is preferred. Since oxotitaniumphthalocyanine is a charge generation substance having high chargegenerating efficiency and charge injecting efficiency, it generates agreat amount of charges by absorption of light and efficiently injectsthe generated charges, without accumulating them in the inside thereof,into the charge transportation substance 13. Further, as described abovefor the charge transportation substance 13, the enamine compound of highcharge mobility represented by the general formula (2) is used.Accordingly, since the charges generated from the charge generationsubstance 12 by light absorption are efficiently injected into thecharge transportation substance 13 and transported smoothly, anelectrophotographic photoreceptor of high sensitivity and highresolution can be obtained.

The charge generation substance 12 may be used in combination withsensitizing dyes, for example, triphenylmethane dyes typicallyrepresented by methyl violet, crystal violet, night blue, and Victoriablue, acrydine dyes typically represented by erythrosin, rhodamine B,rhodamine 3R, acrydine orange, and flaveosin, thiazine dyes typicallyrepresents by methylene blue and methylene green, oxazine dyes typicallyrepresented by capri blue and merdora blue, cyanine dyes, stylyl dyes,pyrylium salt dyes, or thiopyrylium salt dyes.

The method of forming the charge generation layer 15 includes a methodof vacuum vapor depositing the charge generation substance 12 on theouter circumferential surface of the electroconductive substrate 11, ora method of coating a coating solution for charge generation layerobtained by dispersing the charge generation substance 12 in anappropriate solvent to the outer circumferential surface of theelectroconductive substrate 11. Among them, a preferred method includesdispersing the charge generation substance 12 into a binder resinsolution obtained by mixing a binder resin as a binder into anappropriate solvent by a known method to prepare a coating solution forcharge generation layer and coating the obtained coating solution to theouter circumferential surface of the electroconductive substrate 11. Themethod is to be described below.

The binder resin for the charge generation layer 15 is selected from thegroup consisting, for example, of polyestera resin, polystyrene resin,polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxyresin, silicone resin, acryl resin, methacryl resin, polycarbonateresin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, andpolyvinyl formal resin, as well as copolymer resins containing two ormore of repetitive units constituting the resins described above areused each alone or in admixture of two or more of them. Specificexamples of the copolymer resin include, for example, those insulativeresins such as vinyl chloride-vinyl acetate copolymer resin, vinylchloride-vinyl acetate-maleic acid anhydride copolymer resin, andacrylonitrile-styrene copolymer resin. The binder resin is notrestricted to them but those resins used generally can be used as thebinder resin.

As a solvent for the coating liquid for charge generation layer, forexample, halogenated hydrocarbons such as dichloromethane ordichloroethane, ketones such as acetone, methyl ethyl ketone orcyclohexanone, esters such as ethyl acetate or butyl acetate, etherssuch as tetrahydrofuran (referred to as THF) or dioxane, alkylethers ofethylene glycol such as 1,2-dimethoxyethane, aromatic hydrocarbons suchas benzene, toluene or xylene, or aprotonic polar solvents such asN,N-dimethyl formamide or N,N-dimethylacetoamide, etc, are used. Thesolvents may be used alone or two or more of them may be mixed and usedas a mixed solvent.

As the blending ratio between the charge generation substance 12 and thebinder resin, it is preferred that the ratio of the charge generationsubstance 12 is within a range from 10% by weight to 99% by weight. In acase where the ratio of the charge generation substance 12 is less than10% by weight, the sensitivity is lowered. In a case where the ratio ofthe charge generation substance 12 exceeds 99% by weight, since not onlythe film strength of the charge generation layer 15 is lowered but alsothe dispersibility of the charge generation substance 12 is lowered toincrease coarse particles to sometimes decrease the surface charges atthe portion other than the portion to be erased by exposure, thisincreases image defects, particularly, image fogging referred to as“black speck” where toners are deposited to the white back ground toform fine black spots. Accordingly, it is defined as from 10% by weightto 99% by weight.

Before dispersing the charge generation substance 12 in the binder resinsolution, the charge generation substance 12 may previously bepulverized by a pulverizer. The pulverizer used for pulverizationincludes, for example, a ball mill, sand mill, attritor, vibration mill,and supersonic dispersing machine.

The dispersing machine used upon dispersing the charge generationsubstance 12 into the binder resin solution includes, for example, apaint shaker, ball mill, and sand mill. As the dispersion conditions,appropriate conditions are selected so as not to cause intrusion ofimpurities due to abrasion of members constituting the container ordispersing machine to be used.

The coating method of the coating solution for charge generation layerincludes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method, and dip coating method.Among the coating method described above, since the dip coating methodis particularly excellent with various view points as described above,it has been often utilized also in a case of forming the chargegeneration layer 15. As the apparatus used for the dip coating method, acoating solution dispersing apparatus typically represented by asupersonic generation apparatus may be provided in order to stabilizethe dispersibility of the coating solution.

The film thickness of the charge generation layer 15 is, preferably,0.05 μm or more and 5 μm or less and, more preferably, 0.1 μm or moreand 1 μm or less. In a case where the film thickness of the chargegeneration layer 15 is less than 0.05 μm, the light absorptionefficiency is lowered to lower the sensitivity. In a case where the filmthickness of the generation layer 15 exceeds 5 μm, the charge transferin the charge generation layer constitutes a rate determining step inthe process of erasing charges on the surface of the photoreceptor tolower the sensitivity. Accordingly, it is defined as 0.05 μm or more and5 μm or less.

As the electroconductive material constituting the electroconductivesubstrate 11, metal materials, for example, elemental metals such asaluminum, copper, zinc, and titanium, as well as alloys such as aluminumalloys and stainless steels can be used. Further, with no particularrestriction to such metal materials, polymeric materials such aspolyethylene terephthalate, nylon, or polystyrene, hard paper or glassin which metal foils are laminated, metal materials are vapor deposited,or a layer of electroconductive compound such as electroconductivepolymer, tin oxide, or indium oxide is vapor deposited or coated on thesurface thereof can also be used. While the shape of theelectroconductive substrate 11 is cylindrical in this embodiment, it isnot restrictive but may be a circular columnar shape, sheet like shape,or endless belt shape.

The surface of the electroconductive substrate 11 may optionally beapplied with an anodizing treatment, a surface treatment with chemicalsor hot water, a coloring treatment or a random reflection treatment, forexample, by surface roughening, within a range not affecting the picturequality. In the electrophotographic process using laser as an exposuresource, since the wavelength of laser beams is coherent, the incidentlaser light and the light reflected in the photoreceptor may sometimescause interference and the interference fringe caused by interferenceappears on the images to result in image defects. Image defects by theinterference of the laser light of coherent wavelength can be preventedby applying the treatment described above to the surface of theelectroconductive substrate 11.

FIG. 2 is a schematic cross sectional view schematically showing theconstitution of an electrophotographic photoreceptor according to asecond embodiment of the invention. The electrophotographicphotoreceptor 2 in this embodiment is similar with theelectrophotographic photoreceptor 1 of the first embodiment, andcorresponding portions carry identical references, for which explanationis to be omitted.

What is to be noted in the electrophotographic photoreceptor 2 isprovision of an intermediate layer 18 between the electroconductivesubstrate 11 and the photosensitive layer 14.

In a case where the intermediate layer 18 is not present between theelectroconductive substrate 11 and the photosensitive layer 14, chargesare injected from the electroconductive substrate 11 to thephotosensitive layer 14 to lower the chargeability of the photosensitivelayer 14, and the surface charges in the portion other than the portionsto be erased by exposure are decreased to sometimes result in defectssuch as fogging to the images. Particularly, in a case of forming imagesby using a reversal development process, since toner images are formedto the portion decreased with the surface charges by exposure, when thesurface charges are decreased by the factor other than the exposure,toner is deposited to the white background to result in fogging ofimages referred to as black speck in which fine black spots are formedby the deposition of the toner on the white background to remarkablydeteriorate the image qualities. That is, in a case where theintermediate layer 18 is not present between the electroconductivesubstrate 11 and the photosensitive layer 14, this lowers thechargeability in the minute region due to the defects of theelectroconductive substrate 11 or the photosensitive layer 14 to resultin fogging of images such as black specks, which leads to remarkableimage defects.

However, in the electrophotographic photoreceptor 2 in this embodiment,since the intermediate layer 18 is provided between theelectroconductive substrate 11 and the photosensitive layer 14 asdescribed above, injection of charges from the electroconductivesubstrate 11 to the photosensitive layer 14 can be prevented.Accordingly, lowering of the chargeability of the photosensitive layer14 can be prevented to suppress the decrease of the surface charges inthe portion other than the portions to be erased by exposure andoccurrence of defects such as fogging to the images can be prevented.

Further, since the defects at the surface of the electroconductivesubstrate 11 can be covered to obtain a uniform surface by the provisionof the intermediate layer 18, the film forming property of thephotosensitive layer 14 can be improved. Further, peeling of thephotosensitive layer 12 from the electroconductive substrate 11 can besuppressed to improve the adhesion between the electroconductivesubstrate 11 and the photosensitive layer 14.

For the intermediate layer 18, a resin layer formed of various kinds ofresin materials, or an alumite layer is used.

The resin materials forming the resin layer include, those resins suchas polyethylene resin, polypropylene resin, polystyrene resin, acrylresin, vinyl chloride resin, vinyl acetate resin, polyurethane resin,epoxy resin, polyester resin, melamine resin, silicone resin, polyvinylbutyral resin, and polyamide resin, as well as copolymer resinscontaining two or more of repetitive units constituting the resinsdescribed above. Further, casin, gelatin, polyvinyl alcohol, ethylcellulose, etc. can also be used. Among them, use of the polyamide resinis preferred and, particularly, use of alcohol soluble nylon resin ispreferred. Preferred alcohol soluble nylon resin includes, for example,so-called copolymerized nylon formed by copolymerizing 6-nylon,6,6-nylon, 6,10-nylon, 11-nylon and 2-nylon, as well as those resinformed by chemically modifying nylon such as N-alkoxymethyl modifiednylon and N-alkoxyethyl modified nylon.

The intermediate layer 18 may also contain particles such as of metaloxide. Incorporation of the particles can control the volumic resistancevalue of the intermediate layer 18 and improve the effect of preventinginjection of charges from the electroconductive substrate 11 to thephotosensitive layer 14, and can maintain the electric characteristicsof the photoreceptor under various circumstances.

The metal oxide particles include, for example, those particles oftitanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide.

In a case of incorporating particles such as of metal oxides into theintermediate layer 18, the intermediate layer 18 can be formed, forexample, by dispersing the particles into a resin solution formed bydissolving the resin described above into an appropriate solvent toprepare a coating solution for the intermediate layer and coating thecoating solution to the outer circumferential surface of theelectroconductive substrate 11.

As the solvent for the resin solution, water or various kinds of organicsolvents is used. Particularly, a single solvent such as water,methanol, ethanol, or butanol, or mixed solvent comprising such as waterand alcohol, two or more kinds of alcohols, acetone or dioxolane andalcohols, and chlorine solvent such as dichloroethane, chloroform, ortrichloroethane and alcohols are used suitably.

As the method of dispersing the particles in the resin solution, ageneral method of using a ball mill, sand mill, attritor, vibrationmill, or supersonic dispersing machine, etc. can be used.

The total content (C) for the resin and the methyl oxide in the coatingsolution for intermediate layer relative to the content of the solvent(D) in the coating solution for intermediate layer is, preferably, from1/99 to 40/60 and, more preferably, from 2/98 to 30/70 by the weightratio C/D. Further, the ratio between the resin and the metal oxide(resin/metal oxide), is preferably, from 90/10 to 1/99 and, morepreferably, from 70/30 to 5/95 by weight ratio.

The coating method of the coating solution for intermediate layerincludes, for example, a spraying method, a bar coating method, a rollcoating method, a blade method, wringing method, and a dip coatingmethod. Particularly, as previously stated since the dip coating methodis relatively simple and is excellent in view of the productivity andthe cost, it has been often utilized also in a case of forming theintermediate layer 18.

The film thickness of the intermediate layer 18 is, preferably, from0.01 μm or more and 20 μm or less and, preferably, 0.05 μm or more and10 μm or less. In a case where the film thickness of the intermediatelayer 18 is less than 0.01 μm, it no more substantially functions as theintermediate layer 18 and no uniform surface property by coating thedefects of the surface of the electroconductive substrate 11 can beobtained, and injection of charges from the electroconductive substrate11 to the photosensitive layer 14 can not be prevented to lower thechargeability of the photosensitive layer 14. It is not preferred toincrease the film thickness of the intermediate layer 18 to more than 20μm since formation of the intermediate layer 18 is difficult and thephotosensitive layer 14 can not be formed uniformly on the outercircumferential surface of the intermediate layer 18 to lowersensitivity of the photoreceptor in a case of forming the intermediatelayer 18 by the dip coating method.

FIG. 3 is a schematic cross sectional view schematically showing theconstitution of an electrophotographic photoreceptor according to athird embodiment of the invention. The electrophotographic photoreceptor3 in this embodiment is similar with the electrophotographicphotoreceptor 1 of the first embodiment, and corresponding portionscarry identical references, for which explanation is to be omitted.

What is to be noted for the electrophotographic photoreceptor 3 is thatthe photosensitive layer 140 has a single layered structure in which thecharge generation substance 12 and the charge transportation substance13 containing the enamine compound represented by the general formula(2) are bonded by the binder resin 17 containing a polyarylate resinhaving the structural unit represented by the general formula (1). Thatis, the electrophotographic photoreceptor 3 is a single layeredphotoreceptor.

In the electrophotographic photoreceptor 3 of the single layered typedescribed above, the photosensitive layer 140, like the chargetransportation layer 16 provided to the electrophotographicphotoreceptor 1 in the first embodiment, is scraped and worn by thecontacting member used upon transfer of the toner images on the surfaceof the photoreceptor obtained by developing static latent images to therecording medium, or upon removing the toner remaining on the surface ofthe photoreceptor after transfer in the electrophotographic process.

However, since the photosensitive layer 140 provided to theelectrophotographic photoreceptor 3 in this embodiment contains thepolyarylate resin having the structural unit represented by the generalformula (1) of excellent mechanical strength like the chargetransportation layer 16 provided to the electrophotographicphotoreceptor 1 of the first embodiment, the photoreceptor 3 shows asmall wear amount, the wear resistance is excellent and change ofcharacteristics caused by film scraping of the photosensitive layer 140is small.

Further, since the enamine compound represented by the general formula(2) used for the charge transportation substance 13 is excellent in thecompatibility with the polyarylate resin having the structural unitrepresented by the general formula (1) and has high a charge mobility,it is possible to obtain an electrophotographic photoreceptor showinghigh charge potential, high sensitivity and sufficient responsivity,even in a case where the photosensitive layer 140 contains thepolyarylate resin having the structural unit represented by the generalformula (1) and with no deterioration of the electric characteristicseven in a case of repetitive use.

Accordingly, by incorporating the polyarylate resin having thestructural unit represented by the general formula (1) and the enaminecompound represented by the general formula (2) in combination in thephotosensitive layer 140, it is possible to obtain anelectrophotographic photoreceptor excellent in the mechanical strengthand capable of enduring increase in the mechanical stress accompanied todigitalization and increasing resolution of the electrophotographicapparatus, as well as capable of providing favorable electriccharacteristics stably over a long period of time.

The photosensitive layer 140 is formed by the same method as for thecharge transportation layer 16 disposed to the electrophotographicphotoreceptor 1 of the first embodiment described above. For example, itis formed as described below. The charge generation substance 12, thecharge transportation substance 13 containing the enamine compoundrepresented by the general formula (2), and the binder resin 17containing the polyarylate resin having the structural unit representedby the general formula (1) are dissolved or dispersed in the appropriatesolvent described above to prepare a coating solution for photosensitivelayer. The coating solution for photosensitive layer is coated on theouter circumferential surface of the electroconductive substrate 11, forexample, by using a dip coating method.

The ratio (A′/B′) between the charge transportation substance 13 (A′)and the binder resin 17 (B′) in the photosensitive layer 140 ispreferably 10/12 or less by weight ratio in the same manner as the ratio(A/B) between the charge transportation substance 13 (A) and the binderresin (B) in the charge transportation layer 16 provided to theelectrophotographic photoreceptor 1 of the first embodiment. This canimprove the wear resistance of the photoreceptor 140. Further, in a caseof forming the photosensitive layer 140 by the dip coating method, theratio A′/B′ is preferably 10/30 or more by weight ratio.

The film thickness of the photosensitive layer 140 is, preferably, 5 μmor more and 100 μm or less and, more preferably, 10 μm or more and 50 μmor less. In a case where the film thickness of the photosensitive layer140 is less than 5 μm, the charge retainability on the surface of thephotoreceptor is lowered. In a case where the film thickness of thephotosensitive layer 140 exceeds 100 μm, productivity is lowered.Accordingly, it is defined as 5 μm or more and 100 μm or less.

Further, one of more electron accepting materials or dyes may also beadded to the photosensitive layer 14 or the photosensitive layer 140provided to the electrophotographic photoreceptors of first to thirdembodiments described above in order to improve the sensitivity andsuppress the increase of the residual potential and fatigue duringrepetitive use.

As the electron accepting material, electron attracting materials, forexample, acid anhydrides such as succinic acid anhydride, maleic acidanhydride, phthalic acid anhydride, and 4-chloronaphthalic acidanhydride, cyano compound such as tetraethylcyanoethylene and terephthalmalon dinitrile, aldehydes such as 4-nitrobenzoaldehyde, anthraquinonessuch as anthraquinone and 1-nitroanthraquinone, polynuclear orheterocyclic nitro compounds such as 2,4,7-trinitrofluolenone and2,4,5,7-tetranitrofluolenone, as well as diphenoquinone compounds. Thoseformed by making the electron attracting materials to higher molecularweight, etc. may also be used.

As the dyes, organic photoconductive compounds, for example, xanthenedyes, thiazine dyes, triphenylmethane dyes, quinoline pigments, andcopper phthalocyanine can be used. Such organic photoconductivecompounds function as an optical sensitizer.

Further, various kinds of additives such as antioxidant, sensitizer, andUV-ray absorbent may also be added optionally to each of the layers ofthe electrophotographic photoreceptor of first to third embodiments.This can improve potential characteristics. Further, the stability ofthe coating solution upon forming the layer by coating is improved.Further, the fatigue deterioration can be decreased to improve thedurability when the photoreceptor is used repetitively.

Particularly preferred antioxidant includes, for example, phenolcompounds, hydroquinone compounds, tocopherol compounds and aminecompounds. The antioxidant is preferably used within a range from 0.1%by weight or more and 50% by weight or less based on the chargetransportation substance 13. In a case where the amount of theantioxidant to be used is less than 0.1% by weight, no sufficient effectcan be obtained for the improvement of the stability of the coatingsolution and the durability of the photoreceptor. In a case where theamount of the antioxidant to be used exceeds 50% by weight, it gives anundesired effect on the characteristic of the photoreceptor.Accordingly, it is defined as 0.1% by weight or more and 50% by weightor less.

As an electrophotographic apparatus as a fourth embodiment of theinvention, an electrophotographic apparatus 100 having theelectrophotographic photoreceptor 1 of the first embodiment describedabove (photoreceptor 1) is to be exemplified. FIG. 4 is a sideelevational view for the arrangement schematically showing theconstitution of the electrophotographic apparatus 100.

The electrophotographic apparatus 100 comprises a photoreceptor 1rotationally supported on a housing 38, and driving means notillustrated for rotationally driving the photoreceptor 1 around arotational axis 44 in the direction of an arrow 41. The not illustrateddriving means comprises, for example, a motor as a power source androtationally drives the photoreceptor 1 at a predeterminedcircumferential speed by transmitting the power from the motor by way ofnot illustrated gears to a substrate constituting the core of thephotoreceptor 1.

At the periphery of the photoreceptor 1, are disposed a charger 32,not-illustrated exposure means, developing device 33, a transfer roller34, a separation means 37, and a cleaner 36 in this order from theupstream to the downstream in the rotational direction of thephotoreceptor 1 shown by the arrow 41. The cleaner 36 is disposedtogether with a not illustrated charge eliminator. The photoreceptor 1,the charger 32, the developing device 33, and the cleaner 36 aredisposed integrally as to be incorporated in the housing 38 toconstitute a process cartridge 10. The process cartridge 10 isconstituted detachably relative to the electrophotographic apparatusmain body by using not illustrated guide means such a rails.

The charger 32 is the charging means for charging the outercircumferential surface 43 of the photoreceptor 1 to a predeterminedpotential. The charger 32 is, for example, non-contact type chargingmeans, for example, a corona charging system.

The not illustrated exposure means comprise, for example, asemiconductor laser as an optical source and irradiate a light 31 suchas a laser beam outputted from the optical source to the outercircumferential surface 43 of the photoreceptor 1 situated between thecharger 32 and the developing device 33 thereby subjecting the chargedouter circumferentila surface 43 of the photoreceptor 1 to exposure tolight in accordance with image information.

The developing device 33 is developing means for developingelectrostatic latent images formed by exposure to the outercircumferential surface 43 of the photoreceptor 1 by an exposure andcomprise a developing roller 33 a opposed to the photoreceptor 1 andsupplying a toner to the outer circumferential surface 43 of thephotoreceptor 1 and a casing 33 b for rotationally supporting thedeveloping roller 33 a around a rotational axis parallel with therotational axis 44 of the photoreceptor 1 and housing the developercontaining the toner to the inner space thereof.

The transfer roller 34 is transferring means opposed to thephotoreceptor 1 for transferring the developed images to transfer paper51 by contacting the photoreceptor 1 and the transfer paper 51 which isa recording medium supplied between the photoreceptor 1 and the transferroller 34 by not illustrated transferring means in the direction of thearrow 42.

The separation means 37 are means for separating the photoreceptor 1 andthe transfer paper 51 put in press contact.

The cleaner 36 is cleaning means for removing to recover the tonerremaining on the outer circumferential surface 43 of the photoreceptor 1after the transferring operation by the transfer roller 34 and comprisesa cleaning blade 36 a for separating the toner remaining on the outercircumferential surface 43 of the photoreceptor 1 from the outercircumferential surface 43, and a recovery casing 36 b for housing thetoner peeled by the cleaning blade 36 a.

Further, a fixing device 35 as fixing means for fixing imagestransferred on the transfer paper 51 is disposed in the direction wherethe transfer paper 51 separated from the photoreceptor 1 by theseparation means 37 is conveyed. The fixing device 35 comprises aheating roller 35 a having heating means not illustrated and a pressroller 35 b opposed to the heating roller 35 a and pressed by theheating roller 35 a to form a contact portion.

The image forming operation by the electrophotographic apparatus 100 isto be described. At first, when the photoreceptor 1 is drivenrotationally by the driving means in the direction of the arrow 41, theouter circumferential surface 43 of the photoreceptor 1 is uniformlycharged to a predetermined positive or negative potential by the charger32 disposed upstream to the focusing point of the light 31 from theexposure means in the rotational direction of the photoreceptor 1. Then,the light 31 is irradiated from the exposure means to the outercircumferential surface 43 of the photoreceptor 1. The light 31 from thelight source is scanned repetitively in the longitudinal direction ofthe photoreceptor 1 which is a main scanning direction. When thephotoreceptor is rotated and the light from the light source isrepetitively scanned, exposure in accordance with image information isapplied to the outer circumferential surface 43 of the photoreceptor 1.By the exposure, surface charges at the portion irradiated with thelight 31 are eliminated to result a difference between the surfacepotential at the portion irradiated with the light 31 and the surfacepotential at the portion not irradiated with the light 31, to formelectrostatic latent images to the outer circumferential surface 43 ofthe photoreceptor 1. Then, toner is supplied to the outercircumferential surface 43 of the photoreceptor 1 formed with theelectrostatic latent images from the developing roller 33 a of thedeveloping device 33 located downstream to the focusing point of thelight 31 from the light source in the rotationally direction of thephotoreceptor 1 to develop electrostatic latent images, and toner imagesare formed to the outer circumferential surface 43 of the photoreceptor1.

Further, in synchronization with exposure to the photoreceptor 1,transfer paper 51 is fed by conveying means in the direction of thearrow 42 between the photoreceptor 1 and the transfer roller 34 locateddownstream to the developing device 33 in the rotational direction.

When the transfer paper 51 is fed between the photoreceptor 1 and thetransfer roller 34, the transfer roller 34 is pressed to thephotoreceptor 1 to form a contact portion. Thus, the photoreceptor landthe transfer paper 51 are in press contact and the toner images formedon the outer circumferential surface 43 of the photoreceptor 1 aretransferred onto the transfer paper 51.

The transfer paper 51 transferred with the toner images are peeled fromthe outer circumferential surface 43 of the photoreceptor 1 by theseparation means 37, then conveyed by not illustrated conveying means tothe fixing device 35 and heated and pressed upon passage through thecontact portion between the heating roller 35 a and the press roller 35b of the fixing device 35. Thus, the toner images on the transfer paper51 are fixed to the transfer paper 51 as firm images. The transfer paper51 thus formed with the images are discharged by the conveying means tothe outside of the electrophotographic apparatus 100.

On the other hand, a toner remaining on the outer circumferentialsurface 43 of the photoreceptor 1 after the transferring operation bythe transfer roller 34 is peeled from the outer circumferential surface43 of the photoreceptor 1 by the cleaning blade 36 a of the cleaner 36located further downstream to the separation means 37 in the rotationaldirection and upstream to the charger 32 in the rotational direction andrecovered in the recovery casing 36 b. Electric charges on the outercircumferential surface 43 of the photoreceptor 1 removed with the tonerare eliminated by a not illustrated charge eliminator, and theelectrostatic latent images on the outer circumferential surface 43 ofthe photoreceptor 1 are erased. Then, the photoreceptor 1 is furtherrotated and a series of operations starting from charging for thephotoreceptor 1 are repeated again. As described above, images areformed continuously.

As described above since the photoreceptor 1 provided toelectrophotographic apparatus 100 of this embodiment has aphotosensitive layer 14 containing the polyarylate resin having thestructural unit represented by the general formula (1) excellent in themechanical strength and the enamine compound represented by the generalformula (2) of high charge mobility, it is excellent in the mechanicalstrength, capable of enduring increase in the mechanical stress causedby digitalization and increasing resolution of the electrophotographicapparatus and can provide favorable electric characteristics stably fora long period of time. Accordingly, it is possible to obtain anelectrophotographic apparatus with high reliability capable of providinghigh quality images over a long period of time.

Further, while the transfer roller 34 is pressed to the photoreceptor 1as described above, since the photosensitive layer 14 provided to thephotoreceptor 1 contains the polyarylate resin having the structuralunit represented by the general formula (1) of excellent mechanicalstrength as described above, the wear amount of the photosensitive layer14 is small and injuries scarcely occur at the surface of thephotosensitive layer 14. Accordingly, since the pressing force by thetransfer roller 34 can be increased to improve the transfer efficiencyto the transfer paper 51, high quality image with less image defectssuch as whitening or blackening can be provided.

Further, the process cartridge 10 integrally comprises the photoreceptor1, the charger 32, the developing device 33, and the cleaner 36 and isadapted detachably to the electrophotographic apparatus main body.Accordingly, it is not necessary to attach or detach the photoreceptor1, the charger 32, the developing device 33 and the cleaner 36individually to or from the electrophotographic apparatus main body,they can be easily attached or detached to or from theelectrophotographic apparatus main body. Further, as describe above,since the photoreceptor 1 provided to the process cartridge 10 isexcellent in the mechanical strength and can endure the increase of themechanical stress accompanied to digitalization and increasingresolution of the electrophotographic apparatus, as well as can providefavorable electric characteristics stably for a long period of time, aprocess cartridge not requiring exchange for a long period of time canbe obtained.

As has been described above, while the electrophotographic apparatus 100of this embodiment has the electrophotographic photoreceptor 1 of thefirst embodiment but this is not limitative but it may be provided withthe electrophotographic photoreceptor 2 of the second embodiment or theelectrophotographic photoreceptor 3 of the third embodiment.

Further, while the process cartridge 10 comprises integrally thephotoreceptor 1, the charger 32, the developing device 33, and thecleaner 36, they are not limitative but may integrally comprise one ortwo means selected from the group consisting of the photoreceptor 1, thecharger 32, the developing device 33 and the cleaner 36 integrally.

Further, the charger 32 is a non-contact type charging means but this isnot limitative but may also be a contact type charging means such as aroller charging system. As described above, since the photoreceptor 1 isexcellent in the wear resistance, it is possible to obtain anelectrophotographic apparatus of high reliability capable of providinghigh quality images for a long period of time even in a case of usingsuch contact type charging means.

EXAMPLE

The present invention is to be described more specifically by way ofexamples but the invention is not restricted to them.

Preparation Example Preparation Example 1 Preparation of ExemplifiedCompound No. 1 Preparation Example 1-1 Preparation of EnamineIntermediate Product

23.3 g (1.0 equivalent amount) of N-(p-tolyl)-α-naphthylaminerepresented by the following structural formula (9), 20.6 g (1.05equivalent amount) of diphenylacetaldehyde represented by the followingstructural formula (10), and 0.23 g (0.01 equivalent amount) ofDL-10-camphor sulfonic acid were added to 100 mL of toluene and heatedto conduct reaction for six hours while removing by-produced water outof the system under azeotropic boiling with toluene. After thecompletion of the reaction, the reaction solution was concentrated toabout 1/10, which was gradually dropped into 100 mL of hexane underviolent stirring to form crystals. The resultant crystals were separatedby filtration and cleaned with cold ethanol to obtain 36.2 g of a paleyellow powdery compound.

As a result of analyzing the obtained compound by liquidchromatography-mass spectrometry (simply referred to as: LC-MS), since apeak corresponding to a molecular ion [M+H]⁺ formed by adding a protonto the enamine intermediate product shown by the following structuralformula (11) (calculated value for the molecular weight: 411.20) wasobserved at 412.5, it was found that the resultant compound is anenamine intermediate product represented by the following structuralformula (11) (yield: 88%). Further from the result of LC-MS analysis, itwas found that the purity of the obtained enamine intermediate

As described above, an enamine intermediate product represented by thestructural formula (11) could be obtained by conducting dehydratingcondensation reaction between N-(p-tolyl)-α-naphthylamine represented bythe structural formula (9) as a secondary amine compound anddiphenylacetaldehyde represented by the structural formula (10) as analdehyde compound.

Preparation Example 1-2 Preparation of Enamine-aldehyde IntermediateProduct

9.2 g (1.2 equivalent amount) of oxyphosphorus chloride was addedgradually under ice cooling into 100 mL of anhydrousN,N-dimethylformamide (DMF), and stirred for about 30 min to prepare aVilsmeier reagent. 20.6 g (1.0 equivalent amount) of the enamineintermediate product represented by the structural formula (11) obtainedin Preparation Example 1-1 under ice cooling into the solutiongradually. Then, it was gradually heated to elevate the reactiontemperature to 80° C. and stirred while heating so as to keep at 80° C.for 3 hours. After the completion of the reaction, the reaction solutionwas allowed to cool and added gradually to 800 ml of an aqueous 4Nsodium hydroxide solution to form precipitates. The resultantprecipitates were separated by filtration, washed with watersufficiently and recrystallized with a mixed solvent of ethanol andethyl acetate to obtain 20.4 g of a powdery yellow compound.

As a result of LC-MS analysis of the obtained compound, since a peakcorresponding to molecular ion [M+H]⁺ with addition of a proton to theenamine-aldehyde intermediate product (calculated value of molecularweight: 439.19) represented by the following structural formula (12) wasobserved at 440.5, it was found that the obtained compound was theenamine-aldehyde intermediate product represented by the followingstructural formula (12) (yield: 93%). Further, from the result of LC-MSanalysis, it was found that the purity of the obtained enamine-aldehydeintermediate product was 99.7%.

As described above, the enamine-aldehyde intermediate productrepresented by the structural formula (12) could be obtained byformulation of the enamine intermediate product represented by thestructural formula (11) by the Vilsmeier reaction.

Preparation Example 1-3 Preparation of Exemplified Compound No. 1

8.8 g (1.0 equivalent amount) of the enamine-aldehyde intermediateproduct represented by the structural formula (12) obtained inPreparation Example 1-2, and 6.1 g (1.2 equivalent amount) of diethylcinnamyl phosphate represented by the following structural formula (13)were dissolved in 80 mL of anhydrous DMF. After adding 2.8 g (1.25equivalent amount) of potassium t-butoxide into the solution at a roomtemperature gradually, it was heated to 50° C. and stirred while heatingso as to keep at 50° C. for 5 hours. After allowing the reaction mixtureto cool, it was poured into excess methanol. Precipitates were recoveredand dissolved in toluene to form a toluene solution. The toluenesolution was transferred to a separation funnel, washed with water andthen an organic layer was taken out and the taken out organic layer wasdried with magnesium sulfate. After drying, the organic layer removedwith solids was concentrated and subjected to silica gel columnchromatography to obtain 10.1 g of yellow crystals.

As a result of LC-MS analysis for the obtained crystals, a peakcorresponding to the molecular ion [M+H]⁺ in which a proton was added tothe aimed the enamine compound of Exemplified Compound No. 1 shown inTable 6 (calculated value for molecular weight: 539.26) was observed at540.5.

Further, when nuclear magnetic resonance (simply referred to as: NMR)spectrum of the obtained crystals in heavy chloroform (chemical formula:CDCl₃), was measured, a spectrum supporting the structure of the enaminecompound of Exemplified Compound No. 1 was obtained. FIG. 5 is ¹H-NMRspectrum for the product of Preparation Example 1-3 and FIG. 6 is a viewshowing, in an enlarged scale, 6 ppm to 9 ppm of the spectrum shown inFIG. 5. FIG. 7 is ¹³C-NMR spectrum according to usual measurement forthe product of Preparation Example 1-3 and FIG. 8 is a view showing inan enlarged scale 6 ppm to 9 ppm of spectrum shown in FIG. 7. FIG. 9 is¹³C-NMR spectrum according to DEPT 135 measurement for the product ofPreparation Example 1-3, and FIG. 10 is a view showing, in an enlargedscale, 110 ppm to 160 ppm of the spectrum shown in FIG. 9. In FIG. 5 toFIG. 10, the abscissa expresses the chemical shift value δ (ppm).Further, in FIG. 5 and FIG. 6, the value described between the signaland the abscissa is a relative integration value for each signal basedon the integration value for the signal shown by reference 500 in FIG. 5being assumed as 3.

The data of LC-MS and the NMR spectrometry confirm that the crystalobtained herein is the enamine compound, Compound No. 1 (yield: 94%). Inaddition, the data of LC-MS further confirm that the purity of theenamine compound, Compound No. 1 obtained herein is 99.8%.

As described above, the enamine compound of Exemplified Compound No. 1shown in Table 6 could be obtained by conducting Wittig-Horner reactionbetween the enamine-aldehyde intermediate product represented by thestructural formula (12) and diethyl cinnamyl phosphate represented bythe structural formula (13) as the Wittig reagent.

Preparation Example 2 Preparation of Exemplified Compound No. 61

The enamine intermediate product was prepared by dehydratingcondensation reaction (yield: 94%) and the enamine-aldehyde intermediateproduct was prepared by Vilsmeier reaction (yield: 85%) in the samemanner as in Preparation Example 1 except for using 4.9 g (1.0equivalent amount) of N-(p-methoxyphenyl)-α-naphthylamine instead of23.3 g (1.0 equivalent amount) of N-(p-tolyl)-α-naphthylaminerepresented by the structural formula (9) and, further, Wittig-Hornerreaction was conducted to obtain 7.9 g of a powdery yellow compound. Therelation of the equimolar amount between the reagent and the substrateused in each of the reactions is identical with the relation ofequimolar amount between the reagent and the substrate used inPreparation Example 1.

As a result of LC-MS analysis for the obtained compound, a peakcorresponding to the molecular ion [M+H]⁺ in which a proton was added tothe aimed enemine compound of Exemplified Compound No. 61 shown in Table14 (calculated value for molecular weight: 555.26) was observed at556.7.

Further, when NMR spectrum of the obtained crystals in heavy chloroform(chemical formula: CDCl₃) was measured, a spectrum supporting thestructure of the enamine compound of the Exemplified Compound No. 61 wasobtained. FIG. 11 is ¹H-NMR spectrum for the product of PreparationExample 2 and FIG. 12 is a view showing, in an enlarged scale, 6 ppm to9 ppm of the spectrum shown in FIG. 11. FIG. 13 is ¹³C-NMR spectrumaccording to usual measurement for the product of Preparation Example 2and FIG. 14 is a view showing, in an enlarged scale, 110 ppm to 160 ppmof spectrum shown in FIG. 13. FIG. 15 is ¹³C-NMR spectrum according toDEPT 135 measurement for the products of Preparation Example 2 and FIG.16 is a view showing, in an enlarged scale, 110 ppm to 160 ppm of thespectrum shown in FIG. 15. In FIG. 11 to FIG. 16, the abscissa expressesthe chemical shift value δ (ppm). Further, in FIG. 11 and FIG. 12, thevalue described between the signal and the abscissa is a relativeintegration value for each signal based on the integration value for thesignal shown by Reference 501 in FIG. 11 being assumed as 3.

The data of LC-MS and the NMR spectrometry confirm that the compoundobtained herein is the enamine compound, Compound No. 61 (yield: 92%).In addition, the data of LC-MS further confirm that the purity of theenamine compound, Compound No. 61 obtained herein is 99.0%.

As in the above, the three-stage reaction process that comprisesdehydrating condensation, Vilsmeier reaction and Wittig-Horner reactiongives the enamine compound, Compound No. 61 shown in Table 9, and theoverall three-stage yield of the product was 73.5%.

Preparation Example 3 Preparation of Exemplified Compound No. 46

2.0 g (1.0 equivalent amount) of the enamine-aldehyde intermediateproduct represented by the structural formula (12) obtained inPreparation Example 1-2, and 1.53 g (1.2 equivalent amount) of a Wittigreagent represented by the following structural formula (14) weredissolved in 15 mL of anhydrous DMF. After adding 0.71 g (1.25equivalent amount) of potassium t-butoxide into the solution at a roomtemperature gradually, it was heated to 50° C. and stirred while heatingso as to keep at 50° C. for 5 hours. After allowing the reaction mixtureto cool, it was poured into excess methanol. Precipitates were recoveredand dissolved in toluene to form a toluene solution. The toluenesolution was transferred to a separation funnel, washed with water andthen an organic layer was taken out and the organic taken out was driedwith magnesium sulfate. After drying, the organic layer removed withsolids was concentrated and subjected to silica gel columnchromatography to obtain 2.37 g of yellow crystals.

Thus obtained, the crystal was analyzed through LC-MS, which gave a peakat 566.4 corresponding to the molecular ion [M+H]⁺ of the intendedenamine compound, Compound No. 46 in Table 7 (calculated molecularweight: 565.28) with a proton added thereto. This confirms that thecrystal obtained herein is the enamine compound, Compound No. 46 (yield:92%). In addition, the data of LC-MS further confirm that the purity ofthe enamine compound, Compound No. 46 is 99.8%.

As described above, the enamine compound of Exemplified Compound No. 46shown in Table 12 could be obtained by conducting Wittig-Horner reactionbetween the enamine-aldehyde intermediate product represented by thestructural formula (12) and the Wittig reagent represented by thestructural formula (14).

Comparative Preparation Example 1 Preparation of Compound

represented by the following structural formula (15)

2.0 g (1.0 equivalent amount) of the enamine-aldehyde intermediateproduct represented by the structural formula (12) obtained inPreparation Example 1-2 was dissolved in 15 mL of anhydrous THF, and5.23 mL (1.15 equivalent amount) of a THF solution of aryl magnesiumbromide as a Grignard reagent prepared from aryl bromide and metallicmagnesium (mol concentration: 1.0 mol/L) was gradually added at 0° C. inthe solution. After stirring at 0° C. for 0.5 hours, when the proceedingstate of the reaction was confirmed by thin layer chromatography, nodistinct reaction products could be confirmed and plural products wereconfirmed. After conducting post treatment, extraction and condensationby a customary method, silica gel column chromatography was conducted toseparate and purify the reaction mixture.

However, the aimed compound represented by the following structuralformula (15) could not be obtained.

Example Example 1 Example 1-1

After adding one part by weight of an X-type non-metal phthalocyanine asa charge generation substance 12 in a resin solution obtained bydissolving one part by weight of a polyvinyl butyral resin (manufacturedby Sekisui Chemical Industry Co: S-LEC BX-1) into 98 parts by weight oftetrahydrofuran (THF), they were dispersed by a paint shaker for 2 hoursto prepare a coating solution for charge generation layer. After coatingthe coating solution for charge generation layer on aluminum of apolyester film of 80 μm thickness as an electroconductive substrate 11vapor deposited with aluminum on the surface thereof by a bakerapplicator, it was dried to form a charge generation layer 15 of 0.3 μmfilm thickness.

Then, 8 parts by weight of the enamine compound of Exemplified CompoundNo. 1 shown in Table 6 as the charge transportation substance 13 and 10parts by weight of a polyarylate resin having the structural unitrepresented by the structural formula (1-3) shown in Table 1 as thebinder resin 17 (viscosity average molecular weight 23,200) weredissolved in a mixed solvent of 40 parts by weight of tetrahydrofuranand 40 parts by weight of toluene, to prepare a coating solution forcharge transportation layer. After coating the coating solution forcharge transportation layer on the previously formed charge generationlayer 15 by a baker applicator, it was dried to form a chargetransportation layer 16 of 20 μm film thickness.

As described above, a stacked type electrophotographic photoreceptor ofthe layer constitution shown in FIG. 1 satisfying the conditions of theinvention was manufactured.

Example 1-2

A sample for measuring the charge mobility was manufactured in the samemanner as in Example 1-1 except for forming the charge transportationlayer 16 such that the film thickness was 10 μm.

Examples 2 to 6

Five types of electrophotographic photoreceptors and samples formeasuring charge mobility capable of satisfying the conditions of theinvention were manufactured in the same manner as in Example 1 exceptfor using, instead of the Exemplified Compound No. 1, the enaminecompounds of Exemplified Compound No. 3 shown in Table 6, ExemplifiedCompound No. 61 shown in Table 14, Exemplified Compound No. 106 shown inTable 21, Exemplified Compound No. 146 shown in Table 26, andExemplified Compound No. 177 shown in Table 31 as the chargetransportation substance 13.

Example 7

One part by weight of X-type non-metal phthalocyanine as the chargegeneration substance 12, 12 parts of the polyarylate resin (viscosityaverage molecular weight: 23,200) having the structural unit representedby the structural formula (1-3) shown in Table 1 as the binder resin 17,10 parts by weight of the enamine compound of Exemplified Compound No. 1shown in Table 6 as the charge transportation substance 13, 5 parts byweight of 3,5-dimethyl-3′,5′-di-t-butyldiphenoquinine, 0.5 parts byweight of 2,6-di-t-butyl-4-methylphenol, and 65 parts by weight of THFwere dispersed in a ball mill for 12 hours to prepare a coating solutionfor photosensitive layer. After coating the prepared coating solutionfor photosensitive layer on aluminum of a polyester film of 80 μmthickness vapor deposited with aluminum on the surface thereof as theelectroconductive substrate 11 by a baker applicator, it was dried byhot blow at 110° C. for one hour to form a photosensitive layer 140 of20 μm film thickness.

As described above, a single-layered type electrophotographicphotoreceptor of the layer constitution shown in FIG. 3 satisfying theconditions of the invention was manufactured.

Example 8

An electrophotographic photoreceptor satisfying the conditions of theinvention was manufactured in the same manner as in Example 1-1 exceptfor using, instead of the polyarylate resin having the structural unitrepresented by the structural formula (1-3), 10 parts by weight of apolyarylate resin having the structural unit represented by thestructural formula (1-2) shown in Table 1 (viscosity average molecularweight: 35,000) as the binder resin 17 for the charge transportationlayer 16.

Comparative Example 1

An electrophotographic photoreceptor not satisfying the conditions ofthe invention was manufactured in the same manner as in Example 1-1except for using, instead of the polyarylate resin having the structuralunit represented by the structural formula (1-3), 10 parts by weight ofa bisphenol A polycarbonate resin (Panlite C-1400, manufactured byTeijin Chemicals Ltd.) as the binder resin 17 for the chargetransportation layer 16. In the followings, the bisphenol Apolycarbonate resin is sometimes referred to as PCA.

Comparative Example 2

An electrophotographic photoreceptor and a sample for measuring thecharge mobility not satisfying the conditions of the invention weremanufactured in the same manner as in Example 1 except for using,instead of the Exemplified Compound No. 1, a comparative compoundrepresented by the following structural formula (16) as the chargetransportation substance 13. In the followings, the comparative compoundrepresented by the following structural formula (16) is sometimesreferred to as TPD.

Comparative Example 3

An electrophotographic photoreceptor and a sample for measuring thecharge mobility not satisfying the conditions of the invention weremanufactured in the same manner as in Example 1 except for using,instead of the Exemplified Compound No. 1, a comparative compoundrepresented by the following structural formula (17) as the chargetransportation substance 13. In the followings, the comparative compoundrepresented by the following structural formula (17) is sometimesreferred to as ENA.

<Measurement for Charge Mobility>

For each of the samples for measuring the charge mobility manufacturedin Examples 1 to 6 and Comparative Examples 2 and 3 described above,gold was vapor deposited on the surface of the charge transportationlayer and the charge mobility of the charge transportation substance inthe charge transportation layer was measured by a time-of-flight methodat a room temperature under a reduced pressure. Table 38 shows theresult of measurement. The values for the charge mobility shown in Table38 are values at an electric field strength of 2×10⁵ V/cm.

TABLE 38 Charge mobility Sample Charge transportation substance (cm²/V ·sec) Example 1 Exemplified Compound 1 5.74 × 10⁻⁵ Example 2 ExemplifiedCompound 3 5.90 × 10⁻⁵ Example 3 Exemplified Compound 61 5.35 × 10⁻⁵Example 4 Exemplified Compound 106 8.32 × 10⁻⁵ Example 5 ExemplifiedCompound 146 1.64 × 10⁻⁵ Example 6 Exemplified Compound 177 4.20 × 10⁻⁵Comparative TPD 2.24 × 10⁻⁷ Example 2 Comparative ENA 9.68 × 10⁻⁷Example 3

From comparison between Examples 1 to 6 and Comparative Example 2, itwas found that the enamine compound represented by the general formula(2) had a charge mobility higher by two digits or more compared with thecomparative compound (TPD) represented by the structural formula (16) asthe known charge transportation substance.

Further, from comparison between Examples 1 to 6 and Comparative Example3, it was found that the enamine compound represented by the generalformula (2) had a charge mobility higher by two digits or more alsocompared with the comparative compound (ENA) represented by thestructural formula (17) corresponding to a compound in which thenaphthylene group bonded to the nitrogen atom contained in thefunctional group of enamine in the general formula (2) described aboveis substituted with other arylene group.

Further, from comparison between Examples 1 to 3 and 6, and Example 5,it was found that the compound in which Ar³ is a naphthyl group in thegeneral formula (2) had higher charge mobility than the compound inwhich Ar³ is not the naphthyl group.

<Evaluation for Characteristics>

Electric characteristics and wear characteristics were evaluated foreach of the electrophotographic photoreceptors manufactured in Examples1 to 8 and Comparative Examples 1 to 3 described above as shown below.

(Evaluation for Electric Characteristics)

For each of the electrophotographic photoreceptors manufactured inExamples 1 to 8 and Comparative Examples 1 to 3, initial characteristicsand characteristics after repetitive use were evaluated by using anelectrostatic copy paper test apparatus (manufactured by Kawaguchi DenkiSeisakusho Co: EPA-8200).

The initial characteristics were evaluated as described below. Thesurface of the photoreceptor was charged by applying a voltage atnegative (−)5 kV to a photoreceptor and the surface potential on thephotoreceptor in this case was measured as the charge potential V₀ (V).However, in a case of the single layered type photoreceptor in Example7, a voltage at positive (+)5 kV was applied. Then, exposure was appliedto the charged surface of the photoreceptor. In this case, the energyrequired for decaying the surface potential on the photoreceptor toone-half of the charge potential V₀ was measured as a half-decayexposure amount E_(1/2) (μJ/cm²) and used as the evaluation index forthe sensitivity. Further, the surface potential on the photoreceptor atthe time with lapse of 10 secs. from the start of exposure was measuredas the residual potential V_(r) (V) and used as the evaluation index forlight responsivity. For the exposure, a light at a wavelength of 780 nmand at an exposure energy of 1 μW/cm² obtained by spectralyzing by amonochrometer was used.

The characteristics after repetitive use were evaluated as below. Afterrepeating the operation of the charging and exposure for 5000 times asone cycle, the half-decay exposure amount E_(1/2), the charge potentialV₀, and the residual potential V_(r) were measured in the same manner asin the evaluation for initial characteristics.

(Evaluation for Wear Characteristics)

For each of electrophotographic photoreceptors manufactured in Examples1 to 8 and Comparative Examples 1 to 3, wear characteristics wereevaluated by using a wear tester manufactured by Suga Test InstrumentsCo. Evaluation was conducted as below. Friction was applied for 2000cycles to each of the photoreceptors using aluminum oxide #1000 as anabrasion material under a load of 1.96N. The difference between theweight of the photoreceptor before friction and the weight of thephotoreceptor after friction for 2,000 cycles was determined as a wearamount (mg). As the value of the wear amount is smaller, it shows moreexcellent wear resistance.

Table 39 shows the result of measurement described above. In Table 39,in a case where the polyarylate resins having the structural unitrepresented by the general formula (1) are used as the binder resin 17,they are indicated by the number of the structural formulae representingthe structural units.

TABLE 39 Charge transportation layer Charge Initial characteristicsCharacteristics after repetitive use Wear transportation Binder E_(1/2)V₀ V_(r) E_(1/2) V₀ V_(r) amount substance resin (μJ/cm²) (V) (V)(μJ/cm²) (V) (V) (mg) Example 1 Exemplified (1-3) 0.10 −583 −11 0.11−574 −14 2.50 Compound 1 Example 2 Exemplified (1-3) 0.12 −582 −13 0.13−575 −16 2.55 Compound 3 Example 3 Exemplified (1-3) 0.10 −585 −10 0.11−574 −13 2.60 Compound 61 Example 4 Exemplified (1-3) 0.10 −587 −10 0.12−575 −13 2.52 Compound 106 Example 5 Exemplified (1-3) 0.12 −584 −120.14 −576 −15 2.47 Compound 146 Example 6 Exemplified (1-3) 0.13 −582−13 0.15 −576 −18 2.53 Compound 177 Example 7 Exemplified (1-3) 0.15+550 +21 0.17 +545 +25 3.05 Compound 1 Example 8 Exemplified (1-2) 0.10−581 −12 0.11 −572 −15 2.70 Compound 1 Comp. Exemplified PCA 0.13 −579−13 0.14 −575 −16 7.23 Example 1 Compound 1 Comp. TPD (1-3) 0.15 −570−35 0.30 −560 −60 2.53 Example 2 Comp. ENA (1-3) 0.13 −572 −30 0.25 −570−55 2.54 Example 3

From the comparison between Examples 1 to 6 and 8, and ComparativeExample 1, it was found that the photoreceptors of Examples 1 to 6, and8 using polyarylate resins having the structural units represented bythe general formula (1) for the binder resin 17 of the chargetransportation layer 16 showed less wear amount and were excellent inthe wear resistance compared with the photoreceptor of ComparativeExample 1 using the polycarbonate resin for the binder resin 17.

Further, from comparison between Examples 1 to 6, 8 and ComparativeExamples 2 and 3, it was found that the photoreceptors of Examples 1 to6 and 8 using the enamine compound represented by the general formula(2) for the charge transportation substance 13 showed less half-decayexposure amount E_(1/2) and higher sensitivity, and excellent in theresponsivity with the residual potential V_(r) being lower in thenegative direction, that is, with less potential difference between theresidual potential V_(r) and a reference potential, compared with thephotoreceptor of Comparative Example 2 using TPD or the photoreceptor ofComparative Example 3 using ENA having the enamine structure representedby the structural formula (17). Further, it was found that thecharacteristics were maintained also in a case of repetitive use.

Further, from comparison between Example 1 and Example 7, it was foundthat the stacked type photoreceptor of Example 1 having photosensitivelayer having a stacked structure of the charge transportation layer andthe charge generation layer had higher sensitivity and were excellent inthe responsivity compared with the single layered photoreceptor ofExample 7 having the photosensitive layer comprising a single layer.

As described above, by incorporating the polyarylate resin having thestructural unit represented by the general formula (1) and the enaminecompound represented by the general formula (2) in combination in thephotosensitive layer, an electrophotographic photoreceptor of excellentmechanical strength and capable of providing favorable electriccharacteristics stably over a long period of time could be obtained.

Example 9

7 parts by weight of titanium oxide (manufactured by Ishihara SangyoCo.: TTO55A), and 13 parts by weight of copolymer nylon resin(manufactured by Toray Co.: Amilan CM8000) were added to a mixed solventof 159 parts by weight of methanol and 106 parts by weight of1,3-dioxolane, dispersed by a paint shaker for 8 hours to prepare acoating solution for intermediate layer. A cylindrical aluminum supportof 30 mm diameter and 322.3 mm length as an electroconductive substrate11 was dipped in a coating tank filled with the obtained coatingsolution for intermediate layer and then pulled up and driedspontaneously to form an intermediate layer 18 of 1 μm film thickness.

Then, one part by weight of oxotitanium phthalocyanine and one part byweight of polyvinyl butyral resin (manufactured by Denki Kagaku KogyoCo.: #6000-C) were mixed with 98 parts by weight of methyl ethyl ketoneand dispersed by a paint shaker to prepare a coating solution for chargegeneration layer. The obtained coating solution for charge generationlayer was filled in a coating tank and put to dip coating on thepreviously formed intermediate layer 18 and dried spontaneously to forma charge generation layer 15 of 0.4 μm film thickness in the same manneras in the intermediate layer 18.

Then, 8 parts by weight of the enamine compound of Exemplified CompoundNo. 1 shown in Table 6 as the charge transportation substance 13, and 10parts by weight of the polyarylate resin having the structural formularepresented by the structural formula (1-3) shown in Table 1 as thebinder resin 17 (viscosity average molecular weight: 23,200) weredissolved in a mixed solvent of 40 parts by weight of tetrahydrofuranand 40 parts by weight of toluene, to prepare a coating solution forcharge transportation layer. The obtained coating layer for chargetransportation layer was filled in a coating tank and, after dip coatingon the previously formed charge generation layer 15, it was dried toform a charge transportation layer 16 of 25 μm film thickness.

As described above, a stacked type electrophotographic photoreceptor ofthe layer constitution shown in FIG. 2 satisfying the conditions of theinvention was manufactured.

Comparative Example 4

An electrophotographic photoreceptor was manufactured in the same manneras in Example 9 except for using, instead of Exemplified Compound No. 1,the comparative compound (TPD) represented by the structural formula(16) as the charge transportation substance 13.

<Evaluation for Image Quality>

Quality of images formed by using the photoreceptors was evaluated foreach of the electrophotographic photoreceptors manufactured in Example 9and Comparative Example 4 described above. The evaluation was conductedas below. Each of the photoreceptors manufactured in Example 9 andComparative Example 4 was mounted respectively to commercially availablecopying machine (manufactured by Sharp Corp.: AR-265FP), to formhalf-tone images on transfer paper. The half-tone images are imagesexpressing the gradation by white and black dots for the dark and lightof the images. The obtained images were observed with naked eyes toevaluate the quality of the images.

Images formed by the copying machine mounting the photoreceptor ofExample 9 using the enamine compound represented by the general formula(2) for the charge transportation substance 13 were favorable imageswith no defects.

On the other hand, a number of white spots were formed in the imagesformed by the copying machine mounting the photoreceptor of ComparativeExample 4 using TPD for the charge transportation substance 13. It isconsidered that this attributable to that TPD was poor in thecompatibility with the polyarylate resin having the structural unitrepresented by the general formula (1) used as the binder resin 17 ofthe charge transportation layer 16.

From the results described above, it can be seen that the enaminecompound represented by the general formula (2) is excellent in thecompatibility with the polyarylate resin having the structural unitrepresented by the general formula (1).

FIG. 17A is a perspective view schematically showing the constitution ofan electrophotographic photoreceptor 201 according to a fifth embodimentof the invention. FIG. 17B is a fragmentary cross sectional viewschematically showing the constitution of an electrophotographicphotoreceptor 201. The electrophotographic photoreceptor 201(hereinafter sometimes simply referred to as “photoreceptor”) comprisesa cylindrical electroconductive substrate 211 formed of anelectroconductive substance and a photosensitive layer 214 disposed onthe outer circumferential surface of the electroconductive substrate211. The photosensitive layer 214 has a stacked structure in which acharge generation layer 215 containing a charge generation substance 212that generates charges by absorption of light and a chargetransportation layer 216 containing a charge transportation substance213 having an ability of accepting and transferring charges generated inthe charge generation substance 212 and a binder resin 217 for bindingthe charge transportation substance 213 are stacked in this order on theouter circumferential surface of the electroconductive substrate 211.That is, the electrophotographic photoreceptor 201 is a stacked typephotoreceptor.

In the charge transportation layer 216, the charge transportationsubstance 213 is bonded to the binder resin 217. As the chargetransportation substance 213, the enamine compound represented by thegeneral formula (2) is used.

Since the enamine compound represented by the general formula (2) has ahigh charge mobility, it is possible to obtain an electrophotographicphotoreceptor having high charge potential and charge retainability andhigh sensitivity, sufficient light responsivity and also excellent inthe durability by incorporating the enamine compound represented by thegeneral formula (2) as the charge transportation substance 213 in thephotosensitive layer 214. Further, since high charge transportationability can be obtained with no incorporation of the polysilane to thephotosensitive layer 214, an electrophotographic photoreceptor of highreliability not suffering from lowering of the characteristics due toexposure to light can be obtained.

Among the enamine compounds represented by the general formula (2),preferred compounds include enamine compounds represented by the generalformula (3).

Since the enamine compound represented by the general formula (3) has aparticularly high charge mobility among the enamine compoundsrepresented by the general formula (2), an electrophotographicphotoreceptor showing further higher light responsivity can be obtainedby using the enamine compound represented by the general formula (3) forthe charge transportation substance 213. Further, since the enaminecompound represented by the general formula (3) can be synthesizedrelatively easily and at a high yield among the enamine compoundsrepresented by the general formula (2), it can be prepared at a reducedcost. Accordingly, the electrophotographic photoreceptor havingexcellent characteristics as described above can be manufactured at areduced production cost.

Further, among the enamine compounds represented by the general formula(1), those compounds particularly excellent in view of characteristics,cost, productivity, etc. include, in the same manner as described above,those in which Ar¹ and Ar² each represents a phenyl group, Ar³represents a phenyl group, tolyl group, p-methoxyphenyl group,biphenylyl group, naphthyl group or thienyl group, at least one of Ar⁴and Ar⁵ represents a phenyl group, p-tolyl group, p-methoxyphenyl group,naphthyl group, thienyl group, or thiazolyl group, each of R¹¹, R¹²,R¹³, and R¹⁴ represents a hydrogen atom, and n is 1.

As the enamine compound represented by the general formula (2), those,for example, selected from the group consisting of the exemplifiedcompounds shown in Table 6 to Table 37 are used each alone or inadmixture of two or more of them.

The enamine compound represented by the general formula (2) can beprepared in the same manner as described above.

The enamine compound represented by the general formula (2) may be usedin admixture with other charge transportation substance in the samemanner described above. Further, it also includes, for example, polymershaving the groups derived from the compounds in the main chain or theside chain, for example, poly-N-vinylcarbazole, poly-1-vinylpyrene, andpoly-9-vinylanthracene.

However, in order to attain the particularly high charge transportationability, it is considered that the entire amount of the chargetransportation substance 213 comprises the enamine compound representedby the general formula (2).

For the binder resin 217 contained in the charge transportation layer216, a polycarbonate resin having a specified diol ingredient is used.

The polycarbonate resin is a polymer having the structural unitrepresented by the following general formula (18) and is synthesizedfrom the diol compound represented by the following general formula(19). The diol compound is a compound having two hydroxyl groups(chemical formula: —OH) in one molecule as shown in the followinggeneral formula (19).

In the general formulae (18) and (19), R²⁰ represents an organic group.

In the structural unit represented by the general formula (18), sincethe moiety for —O—R²⁰—O— is derived from the diol compound representedby the general formula (19), the moiety is referred to as the diolingredient in this specification.

The polycarbonate resin used in this embodiment has the specified diolingredient as described above, and the specified diol ingredient is anasymmetric diol ingredient derived from the asymmetric diol compound.

An asymmetric diol compound is a diol compound having an organic group(—R²⁰—) to which two hydroxyl groups (—OH) are bonded as the main chain,in which the main chain is linearly arranged in the horizontal directionextending to right and left with respect to the drawing, and the twohydroxyl groups are not symmetry with respect to the line including themain chain on the drawing, when expressed by a planar structural formulaas arranged on both ends of the main chain.

Since the polycarbonate resin having the asymmetric diol ingredientshows high solubility to a solvent irrespective that whether the solventis a halogen type organic solvent or non-halogen type organic solvent,even when a coating solution is prepared by using a non-halogen typeorganic solvent in a case of forming the charge transportation layer 216by coating as will be described later, the coating solution containingthe polycarbonate resin having the asymmetric diol ingredient does notgelate, has a favorable film forming property, also exhibits excellentstability and does not gelate even lapse of several days afterpreparation. By the use of the coating solution, productivity of theelectrophotographic photoreceptor can be improved. Further, since thepolycarbonate resin having the asymmetric diol ingredient is excellentin the mechanical strength, it can suppress the occurrence of injurieson the surface of the photosensitive layer and decrease the filmreduction amount of the photosensitive layer 214 to reduce the change ofcharacteristics caused by the wear of the photosensitive layer 214.Furthermore, since the polycarbonate resin having the asymmetric diolingredient is excellent in the insulative property with the volumicresistance of 10¹³ Ω·cm or higher and has high withstanding voltage,satisfactory electric characteristics can be obtained.

On the other hand, in the case of using the polycarbonate resin havingthe asymmetric diol ingredient for the binder resin 217, characteristicssuch as the light responsivity is sometimes lowered. However, in thisembodiment, since the enamine compound of high transferabilityrepresented by the general formula (2) is used for the chargetransportation substance 213, the characteristics described above arenot deteriorated even in a case of use under a low temperaturecircumstance or in a high speed electrophotographic process.

Accordingly, by the incorporation of the enamine compound represented bythe general formula (2) and the polycarbonate resin having theasymmetric diol ingredient in combination in the photosensitive layer214, it is possible to obtain an electrophotographic photoreceptorhaving high charge potential and charge retainability, high sensitivityand sufficient light responsivity, excellent in durability, with nodeterioration of the characteristics even in a case of use under a lowtemperature circumstance or in a high speed electrophotographic processor in a case of light exposure, as well as having high reliability andfavorable productivity.

Among the polycarbonate resins having the asymmetric diol ingredient,preferred are those having the asymmetric diol ingredients derived fromthe asymmetric diol compound represented by the following generalformula (20), that is, those having a structural unit containing theasymmetric diol ingredient represented by the following general formula(I).

In the general formulae (20) and (I), X¹ represents a single bond,—CR²⁹R³⁰—, an alkylene group which may have a substituent, —S—, —O—,—SO₂—, —SO—, or —CO—.

The single bond means herein that benzene rings on both sides of X¹ arebonded directly. Specific examples in which X¹ is the single bond in thegeneral formula (1) include, for example, structural units representedby the structural formulae (22-17) shown in Table 43 to be describedlater.

Further, in —CR²⁹R³⁰—, R²⁹, and R³⁰ each represents a hydrogen atom, ahalogen atom, an alkyl group which may have a substituent, or an arylgroup which may have a substituent. Specific examples for R²⁹ and R³⁰include, in addition to the hydrogen atom, an alkyl group such asmethyl, ethyl, propyl, isopropyl, isobutyl, cyclohexyl, and cycloheptyl,an aryl group such as phenyl and naphthyl, as well as a halogen atomsuch as a fluorine atom, a chlorine atom, and a bromine atom. The alkylgroup preferably has 1 to 7 carbon atoms. The substituent which may bepresent on the alkyl group and the aryl group includes, for example, analkyl group of 1 to 7 carbon atoms such as methyl, ethyl, propyl, andisopropyl, an aryl group such as phenyl and naphthyl, an aralkyl groupsuch as benzyl or phenethyl, an alkoxy group of 1 to 7 carbon atoms suchas methoxy, ethoxy, and propoxy, as well as a halogen atom such as afluorine atom, a chlorine atom, and a bromine atom. The substituents mayjoin to each other to form a ring structure.

R²⁹ and R³⁰ may join to each other to form a ring structure. Specificexamples of —CR²⁹R³⁰— in a case where R²⁹ and R³⁰ join each other andform a ring structure together with carbon atoms (C) to which R²⁹ andR³⁰ are bonded include, for example, bivalent groups formed by removingtwo hydrogen atoms bonded to cyclo carbon atoms of mononuclear orpolynuclear hydrocarbons such as cyclohexylidene, cyclopentylidene,fluorenylilene, and indanylidene.

Further, specific examples of the alkylene group as X¹ include a linearalkylene group such as a 1,2-ethylene group and a 1,3-propylene group,as well as a cyclic alkylene group such as a 1,6-cyclohexylene group.

Further, in the general formulae (20) and (I), R²¹, R²², R²³, R²⁴, R²⁵,R²⁶, R²⁷ and R²⁸ each represents a hydrogen atom, a halogen atom, analkyl group which may have a substituent, an aryl group which may have asubstituent, or an alkoxy group which may have a substituent. Specificexamples for R²¹, R²², R²³, R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸ include, inaddition to the hydrogen atom, an alkyl group such as methyl, ethyl, andcyclohexyl, and an aryl group such as phenyl and naphthyl, an alkoxygroup such as methoxy, ethoxy and propoxy, as well as a halogen atomsuch as a fluorine atom, a chlorine atom and a bromine atom. The alkylgroup preferably has 1 to 7 carbon atoms. The alkoxy group preferablyhas 1 to 7 carbon atoms. The substituent which may be present on thealkyl group, aryl group, and alkoxy group include an alkyl group of 1 to7 carbon atoms such as methyl, ethyl, propyl, and isopropyl, an arylgroup such as phenyl and naphthyl, an aralkyl group such as benzyl andphenethyl, an alkoxy group of 1 to 7 carbon atoms such as methoxy,ethoxy, and propoxy, as well as a halogen atom such as a fluorine atom,a chlorine atom, and a bromine atom. The substituents may join to eachother to form a ring structure.

However, in the general formulae (20) and (I), in a case where R²¹ andR²³; R²² and R²⁴; R²⁵ and R²⁷; and R²⁶ and R²⁸, respectively anidentical groups, X¹ is —CR²⁹R³⁰—, R²⁹ and R³⁰ are groups different fromeach other, or R²⁹ and R³⁰ may join to each other to form a ringstructure, or X¹ is an alkylene group and having two or moresubstituents different from each other or have two or more substituentson different substitution positions.

Further, in the general formulae (20) and (I), in a case where X¹ is—CR²⁹R³⁰—, R²⁹, R³⁰ are identical groups and they do not join to eachother, or in a case where X¹ is an alkylene group and all substituentspresent on the alkylene group are identical groups and they are presenton identical substitution positions, R²¹ and R²³ are groups differentfrom each other, R²² and R²⁴ are groups different from each other, R²⁵and R²⁷ are groups different from each other, or R²⁶ and R²⁸ are groupsdifferent from each other.

Among the polycarbonate resins having the structural unit containing theasymmetric diol ingredient represented by the general formula (1), thosehaving the asymmetric diol ingredient derived from the asymmetric diolcompound, that is, those having the structural unit containing theasymmetric diol ingredient represented by the following the generalformula (II) are used particularly preferably.

In the general formulae (21) and (II), R²¹, R²², R²³, R²⁴, R²⁵, R²⁶,R²⁷, R²⁸, R²⁹, and R³⁰ have the same meanings as those defined for thegeneral formulae (20) and (I).

However, in the general formulae (21) and (II), R²⁹ and R³⁰ are groupsdifferent from each other or join to each other to form a ringstructure.

Since the polycarbonate resin having the structural unit containing theasymmetric diol ingredient represented by the general formula (II) has abulky substituent on the main chain and the packing density of the resinper se is high, it has a particularly high mechanical strength.Accordingly, by using the polycarbonate resin having the structural unitcontaining asymmetric diol ingredient represented by the general formula(II) for the binder resin 217, it is possible to obtain anelectrophotographic photoreceptor particularly excellent in thedurability, with less occurrence of injuries at the surface of thephotosensitive layer and with less film reduction amount of thephotosensitive layer 214.

While specific examples for the polycarbonate resin having theasymmetric diol ingredient include, for example, those having thestructural units containing the asymmetric diol ingredient representedby the structural formulae (22-1) to (22-18) shown in the followingTable 40 to Table 43, the polycarbonate resin having the asymmetric diolingredient is not restricted to them.

TABLE 40 Structural formula (22-1)

Structural formula (22-2)

Structural formula (22-3)

Structural formula (22-4)

Structural formula (22-5)

TABLE 41 Structural formula (22-6) 

Structural formula (22-7) 

Structural formula (22-8) 

Structural formula (22-9) 

Structural formula (22-10)

TABLE 42 Structural formula (22-11)

Structural formula (22-12)

Structural formula (22-13)

Structural formula (22-14)

Structural formula (22-15)

TABLE 43 Structural formula (22-16)

Structural formula (22-17)

Structural formula (22-18)

The polycarbonate resin having the asymmetric diol ingredient may have,for example, those structural units selected from the group consistingof structural units containing the asymmetric diol ingredientsrepresented by the structural formulae (22-1) to (22-18) shown in Table40 to Table 43 described above each alone or by two or more of them.

Further, the polycarbonate resin having the asymmetric diol ingredientpreferably has, in addition to the asymmetric diol ingredient, asiloxane structure further. The siloxane structure is a structurecontaining a siloxane bond (Si—O).

By using the polycarbonate resin having the asymmetric diol ingredientand the siloxane structure for the binder resin 217, the surfacefriction coefficient of the photosensitive layer 214 is decreased toimprove the slidability. Accordingly, since the toner deposited to thesurface of the photosensitive layer tends to be peeled, the transferefficiency upon transferring the toner images formed on the surface ofthe photosensitive layer to the recording medium, or the cleaningproperty for the surface of the photosensitive layer after transfer isimproved to obtain satisfactory images. Further, since paper dusts, etc.causing injuries formed to the surface of the photosensitive layer arealso tended to be peeled, the surface of the photosensitive layer isless injured. Further, even when the cleaning blade is moved slidablyupon removing the toner remaining on the surface of the photosensitivelayer after transfer, since friction and vibration accompanied tophysical contact between the surface of the photosensitive layer and thecleaning blade are small, abnormal sounds referred to as ringing lessoccurs.

The polycarbonate resin having the asymmetric diol ingredient and thesiloxane structure includes, for example, a copolycarbonate resin havingthe structural unit containing the asymmetric diol ingredient and thesiloxane structure represented by the following general formula (23):

In the general formula (23) plural R³¹ each represents a monovalenthydrocarbon group not containing an aliphatic unsaturated bond. Themonovalent hydrocarbon group as R³¹ includes, for example, an alkylgroup which may have a substituent and aryl group which may have asubstituent. Specific examples of the alkyl group as R³¹ include, forexample, an alkyl group of 1 to 6 carbon atoms such as a methyl group,an ethyl group, a propyl group, an isopropyl group, a butyl group, ans-butyl group, a t-butyl group, an isobutyl group, a pentyl group, and ahexyl group. Among them, the methyl group, the ethyl group, the propylgroup, the isopropyl group, the butyl group, the s-butyl group, and thet-butyl group are preferred. Specific examples of the aryl group as R³¹include an aryl group of 6 to 12 carbon atoms such as a phenyl group,naphthyl group, and biphenylyl group. Among all, the phenol group ispreferred.

In the general formula (23), plural R³² each represents an alkyl groupwhich may have a substituent, an alkoxy group which may have asubstituent, an aryl group which may have a substituent, a halogen atomor a hydrogen atom, and plural u each represents an integer of 1 to 4.Specific examples of the alkyl group as R³² include, for example, analkyl group of 1 to 6 carbon atoms such as a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, an s-butylgroup, a t-butyl group, an isobutyl group, a pentyl group, and a hexylgroup. Among them, the methyl group, the ethyl group, the propyl group,the isopropyl group, the butyl group, the s-butyl group, and the t-butylgroup are preferred. Specific examples of the alkoxy group for R³²include, for example, alkoxy group of 1 to 6 carbon atoms such as amethoxy group, an ethoxy group, a propoxy group, an isopropoxy group, abutoxy group, an s-butoxy group, a t-butoxy group, an isobutoxy group, apentyloxy group, and a hexyloxy group. Among them, the methoxy group,the ethoxy group, the propoxy group, and the isopropoxy group arepreferred. Specific examples of the aryl group as R³² include, forexample, an aryl group of 6 to 12 carbon atoms such as a phenyl group, anaphthyl group and a biphenylyl group. Among them, the phenyl group ispreferred. Specific examples of the halogen atom as R³² include afluorine atom, a chlorine atom, a bromine atom, and an iodine atom.Among them, the fluorine atom, the chlorine atom and the bromine atomare preferred.

Further, in the general formula (23), plural Y¹ each represents analkylene group which may have a substituent, or an alkylene oxyalkylenegroup which may have a substituent.

Further, in the general formula (23), Y² represents an alkylene groupwhich may have a substituent, an alkylene oxyalkylene group which mayhave a substituent, or an oxygen atom.

Specific examples of the alkylene group as Y¹ and Y² include, forexample, an alkylene group of 2 to 6 carbon atoms such as an ethylenegroup, a trimethylene group, a tetramethylene group, a pentamethylenegroup, and a hexamethylene group. Among them, the ethylene group,trimethylene group, and the tetramethylene group are preferred. Thealkylene oxyalkylene group as Y¹ and Y² include, for example, analkylene oxyalkylene group of 4 to 10 carbon atoms such as a methyleneoxypropylene group, a methylene oxybutylene group, an ethyleneoxyethylene group, an ethylene oxypropylene group, an ethyleneoxybutylene group, a propylene oxyhexylene group, and a butyleneoxyhexylene group. Among them, the ethylene oxypropylene group andethylene oxybutylene group are preferred.

Further, in the general formula (23), p¹ represents 0 or 1, p²represents 1 or 2, and p³ represents 1 or 2, providing that the sum forp¹, p², and p³ (p¹+p²+p³) is 3. In a case where p³ is 2, plural Y² mayidentical or different.

Further, in the general formula (23), t¹, t², t³, and t⁴ each representsan integer of 0 or more, providing that the sum for t¹, t², t³, and t⁴(t¹+t²+t³+t⁴) is an integer of 0 to 450. t¹ and t² is each preferably aninteger of 1 to 20. The sum for t³ and t⁴ (t³+t⁴) is preferably aninteger of 0 to 100. The sum for t¹, t², t³, and t⁴ (t¹+t²+t³+t⁴) ispreferably an integer of 2 to 100.

The polycarbonate resin having the asymmetric diol ingredient may alsohave the asymmetric diol ingredient and other structure than thesiloxane structure within a range not deteriorating the effect of theinvention.

The polycarbonate resin having the asymmetric diol ingredient has aviscosity average molecular weight, preferably, from 10,000 or more to70,000 or less, and, more preferably, 30,000 or more to 60,000 or less.In a case where the viscosity average molecular weight of thepolycarbonate resin having asymmetric diol ingredient is less than10,000, the mechanical strength is remarkably weakened to form aphotoreceptor with large film reduction amount of the photosensitivelayer 14 and sensitive to injuries. In a case where the viscosityaverage molecular weight of the polycarbonate resin having theasymmetric diol ingredient exceeds 70,000, the viscosity is excessivelyhigh upon preparation of the coating solution tending to cause coatingunevenness. Accordingly, it is defined as 10,000 or more and 70,000 orless.

The polycarbonate resin having the asymmetric diol ingredient can beprepared by a method used generally upon preparing a polycarbonate resinfrom a diol compound, that is, a phosgene method or an ester exchangemethod.

As the binder resin 217, a polycarbonate resin having the asymmetricdiol ingredient may be used alone, or two or more polycarbonate resinshaving different asymmetric diol ingredients may be used in admixture.

Further, the polycarbonate resin having the asymmetric diol ingredientmay be used being mixed with other resin for the binder resin 217. Asthe other resin used in admixture with the polycarbonate resin havingthe asymmetric diol ingredient, those excellent in the compatibilitywith the charge transportation substance 213 are used. For example, oneor more resins selected from the group consisting of polyarylate,polyvinyl butyral, polyamide, polyester, epoxy resin, polyurethane,polyketone, polyvinyl ketone, polystyrene, polyacrylamide, phenol resin,phenoxy resin, and polysulfone resin, as well as copolymer resinsthereof can be used in admixture with the polycarbonate resin having theasymmetric diol ingredient described above. Among the resins describedabove, since the resin such as polystyrene, polyarylate or polyester isexcellent in the insulation property with the volume resistivity of 10¹³Ω·cm or higher like the polycarbonate resin having the asymmetric diolingredient described above, and is also excellent in the film formingproperty and the potential characteristic, it is preferred to use suchresin.

In a case of use being mixed with other resin, it is preferred that thepolycarbonate resin having the asymmetric diol ingredient isincorporated by 5% by weight or more and 95% by weight or less and, morepreferably, by 10% by weight or more and 90% by weight or less for theentire amount of the binder resin 217.

In the charge transportation layer 216, the ratio A/B for the chargetransportation substance 213 (A) and the binder resin 217 (B) is,preferably, from 10/12 to 10/30 by weight ratio. In a case of using theknown charge transportation substance, the ratio A/B is about 10/12since the light responsivity may sometimes be lowered in a case wherethe ratio of the binder resin 217 is increased as being 10/12 or lessfor the ratio A/B. However, in the electrophotographic photoreceptor 1in this embodiment, since the charge transportation substance 213contains the enamine compound represented by general formula (2) of highcharge mobility, the light responsivity can be maintained even when thebinder resin is added at a higher ratio than in the case of using theknown charge transportation substance, with the ratio A/B being 10/12 to10/30. That is, the binder resin 217 containing the polycarbonate resinhaving the asymmetric diol ingredient can be incorporated at a highconcentration to the charge transportation layer 216 without loweringthe light responsivity. Accordingly, since the printing resistance ofthe charge transportation layer 216 can be improved and the change ofcharacteristics caused by the wear of the photosensitive layer 214 canbe suppressed, the durability of the electrophotographic photoreceptorcan be improved. In addition, since the polycarbonate resin having theasymmetric diol ingredient contained in the binder resin 217 exhibitshigh solubility to a solvent irrespective that the solvent is a halogentype organic solvent or a non-halogen type organic solvent as describedabove, the coating solution is not gelled but stable even in a casewhere the binder resin 217 is added at a such a high ratio and anelectrophotographic photoreceptor can be produced efficiently for a longperiod of time.

In a case where the ratio A/B exceeds 10/12 to lower the ratio of thebinder resin 217 excessively, the printing resistance of the chargetransportation layer 216 is lowered to increase the film reductionamount of the photosensitive layer 214 compared with a case where theratio of the binder resin 217 is high even in a case of using apolycarbonate resin having the asymmetric diol ingredient excellent inthe mechanical strength as described above. Further, in a case where theratio A/B is less than 10/30 to increase the ratio of the binder resin217 excessively, since the viscosity of the coating solution increasesin a case of forming the charge transportation layer 216 by the dipcoating method to be described later, the coating speed is lowered toremarkably worsen the productivity. Further, in a case of increasing theamount of the solvent in the coating solution in order to suppress theincrease of the viscosity of the coating solution, a brushing phenomenonoccurs to cause clouding in the formed charge transportation layer 216.Accordingly, it was defined as 10/12 to 10/30.

An additive such as a plasticizer or a leveling agent may also be addedto the charge transportation layer 216 optionally in order to improvethe film forming property, flexibility and surface smoothness. Theplasticizer include, for example, a dibasic acid ester such as phthalateester, fatty acid ester, phosphate ester, chlorinated paraffin, andepoxy plasticizer. The leveling agent include, for example, siliconetype leveling agent.

Fine particles of an inorganic compound or an organic compound may beadded to the charge transportation layers 216 in order to increase themechanical strength or improve the electric characteristics.

Further, various additives such as an antioxidant and a sensitizer maybe added optionally to the charge transportation layer 216. This canimprove potential characteristics. Further, the stability of the coatingsolution upon forming the charge transportation layer 216 by coating isimproved as will be described later. Further, this can mitigate thefatigue deterioration to improve the durability upon repetitive use ofthe photoreceptor.

As the antioxidant, hindered phenol derivatives or hindered aminederivatives are used preferably. The hindered phenol derivatives arepreferably used within a range of 0.1% by weight or more and 50% byweight or less relative to the charge transportation substance 213.Further, the hindered amine derivatives are used preferably within arange from 0.1% by weight or more and 50% by weight or less relative tothe charge transportation substance 213. The hindered phenol derivativeand the hindered amine derivative may be used in admixture. In thiscase, the total amount of the hindered phenol derivative and thehindered amine derivative to be used is preferably within a range from0.1% by weight or more to 50% by weight or less relative to the chargetransportation substance 213. In a case where the amount of the hinderedphenol derivative to be used, the amount of the hindered aminederivative to be used, or the total amount of the hindered phenolderivative and the hindered amine derivative to be used is less than0.1% by weight, no sufficient effect can be obtained for the improvementof the stability of the coating solution and the improvement of thedurability of the photoreceptor. Further, if the amount exceeds 50% byweight, this gives an undesired effect on the characteristics of thephotoreceptor. Accordingly, it is defined as 0.1% by weight or more and50% by weight or less.

The charge transportation layer 216 is formed, for example, bydissolving or dispersing, in an appropriate solvent, the chargetransportation substance 213 containing the enamine compound representedby the general formula (18) described above and the binder resin 17containing the polycarbonate resin having asymmetric diol ingredient,and the additives described above, if necessary, to prepare a coatingsolution for a charge transportation layer, and coating the obtainedsolution on the outer circumferential surface of the charge generationlayer 215.

As the solvent for the coating solution for charge transportation layer,those selected, for example, from the group consisting of aromatichydrocarbons such as benzene, toluene, xylene, and monochlorobenzene,halogenated hydrocarbons such as dichloromethane and dichloroethane,ether such as tetrahydrofuran, dioxane, and dimethoxymethyl ether, aswell as non-protonic polar solvents such a N,N-dimethylformamide areused each alone or in admixture of two or more of them. Further, ifnecessary, a solvent such as alcohols, acetonitriles, or methyl ethylketone may further be added to the solvent described above and used.However, among the solvent described above, use of the non-halogen typeorganic solvent is preferred in view of the global environment. Asdescribed above, since the polycarbonate resin having the asymmetricdiol ingredient exhibits a high solubility to the solvent irrespectivethat the solvent is a halogen type organic solvent or a non-halogen typeorganic solvent, even when the coating solution is prepared by using thenon-halogen type organic solvent, the coating solution is not gelled,satisfactory in the film forming property and in the stability, and isnot gelled even after lapse of several days from preparation.

The coating method for the coating solution for charge transportationlayer includes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method or dip coating method.Among the coating methods described above, an optimal method can beselected while taking the physical properties of the coating and theproductivity into consideration. Among the coating methods describedabove, since the dip coating method is a method of dipping a substrateinto a coating bath filled with the coating solution and then pulling upthe substrate at a constant speed or at a gradually changing speed toform a layer on the surface of the substrate and, since the method isrelatively simple and excellent in view of the productivity and thecost, it has been often utilized in a case of producing anelectrophotographic photoreceptor and also often utilized in a case offorming the charge transportation layer 216.

The film thickness of the charge transportation layer 216 is preferably,5 μm or more and 50 μm or less and, more preferably, 10 μm or more and40 μm or less. In a case where the film thickness of the chargetransportation layer 216 is less than 5 μm, the charge retainability onthe surface of the photoreceptor is lowered. In a case where the filmthickness of the charge transportation layer 216 exceeds 50 μm,resolution of the photoreceptor is lowered. Accordingly, it is definedas 5 μm or more and 50 μm or less.

As described above, the photosensitive layer 214 has a stacked structureof the charge generation layer 215 containing the charge generationsubstance 212 and the charge transportation layer 216 containing thecharge transportation substance 213. By sharing the charge generatingfunction and the charge transporting function respectively to separatelayers, since optimal materials can be selected for the chargegenerating function and the charge transporting function respectively, aphotoreceptor having higher sensitivity and of high durability furtherimproved stability upon repetitive use can be obtained.

The charge generation layer 215 contains the charge generation substance212 as a main ingredient. The material effective as the chargegeneration substance 212 includes azo pigments such as a monoazopigment, bisazo pigment, and trisazo pigment, indigo pigments such asindigo and thioindigo, perylene pigments such as peryleneimide andperylenic acid anhydride, polynuclear quinone pigments such asanthraquinone and pyrenequinone, phthalocyanine pigments such as metalphthalocyanine and non-metal phthalocyanine, squarylium dyes, pyryliumsalts and thiopyrylium salts, triphenylmethane dyes, and inorganicmaterials such as selenium and amorphous silicon. The charge generationsubstances are used each alone or two or more of them in combination.

Among the charge generation substances described above, use ofoxotitanium phthalocyanine is preferred. Since oxotitaniumphthalocyanine is a charge generation substance having high chargegenerating efficiency and charge injecting efficiency, it generates agreat amount of charges by absorption of light and efficiently injectsthe generated charges, without accumulating them in the inside thereof,into the charge transportation substance 213. Further, for the chargetransportation substance 213, since the enamine compound of high chargemobility represented by the general formula (2) is used, the chargesgenerated from the charge generation substance 212 by light absorptionare efficiently injected into the charge transportation substance 13 andtransferred smoothly. Accordingly, an electrophotographic photoreceptorof high sensitivity and high resolution can be obtained by incorporatingthe enamine compound represented by the general formula (2) and theoxytitanium phthalocyanine to the photosensitive layer 214. Further,while an infrared laser has been used for an exposure light source alongwith digitalization of image forming apparatus in recent years, sincethe oxotitanium phthalocyanine has a maximum absorption peak in thewavelength region of a laser light irradiated from the IR-ray laser,images at high quality can be provided in a digital image formingapparatus with the IR-ray laser being as the exposure light source byusing such an electrophotographic photoreceptor.

The charge generation substance 212 may be used in combination withsensitizing dyes, for example, triphenylmethane dyes typicallyrepresented by methyl violet, crystal violet, night blue, and Victoriablue, acrydine dyes typically represented by erythrosin, rhodamine B,rhodamine 3R, acrydine orange, and flaveosin, thiazine dyes typicallyrepresents by methylene blue and methylene green, oxazine dyes typicallyrepresented by capri blue and merdora blue, cyanine dyes, stylyl dyes,pyrylium salt dyes, or thiopyrylium salt dyes.

The method of forming the charge generation layer 215 includes a methodof vacuum vapor depositing the charge generation substance 212 on theouter circumferential surface of the electroconductive substrate 211, ora method of coating a coating solution for charge generation layerobtained by dispersing the charge generation substance 212 in anappropriate solvent on the outer circumferential surface of theelectroconductive substrate 211. Among them, a preferred method includesdispersing the charge generation substance 212 into a binder resinsolution obtained by mixing a binder resin as a binder into anappropriate solvent by a known method to prepare a coating solution forcharge generation layer and coating the obtained coating solution on theouter circumferential surface of the electroconductive substrate 211.The method is to be described below.

The binder resin for the charge generation layer 215 is selected fromthe group consisting, for example, of polyestera resin, polystyreneresin, polyurethane resin, phenol resin, alkyd resin, melamine resin,epoxy resin, silicone resin, acryl resin, methacryl resin, polycarbonateresin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, andpolyvinyl formal resin, as well as copolymer resins containing two ormore of repetitive units constituting the resins described above areused each alone or in admixture of two or more of them. Specificexamples of the copolymer resin include, for example, those insulativeresins such as vinyl chloride-vinyl acetate copolymer resin, vinylchloride-vinyl acetate-maleic acid anhydride copolymer resin, andacrylonitrile-styrene copolymer resin. The binder resin is notrestricted to them but those resins used generally can be used as thebinder resin. However, among the resins, the polycarbonate resin havingthe asymmetric diol ingredient described above used as the binder resin217 for the charge transportation layer 216 is used preferably. Sincethe polycarbonate resin having the asymmetric diol ingredient exhibits ahigh solubility to the solvent irrespective that the solvent is ahalogen type organic solvent or a non-halogen type organic solvent asdescribed above, a coating solution for charge generation layer which isnot gelled, satisfactory in the film forming property and excellent inthe stability and is not gelled even after lapse of several days frompreparation can be obtained by using the same, to improve theproductivity of the photoreceptor.

As a solvent for the coating solution for charge generation layer, forexample, halogenated hydrocarbons such as dichloromethane ordichloroethane, ketones such as acetone, methyl ethyl ketone orcyclohexanone, esters such as ethyl acetate or butyl acetate, etherssuch as tetrahydrofuran (referred to as THF) or dioxane, alkylethers ofethylene glycol such as 1,2-dimethoxyethane, aromatic hydrocarbons suchas benzene, toluene or xylene, or aprotonic polar solvents such asN,N-dimethyl formamide or N,N-dimethylacetoamide, etc, are used. Thesolvents may be used alone or two or more of them may be mixed and usedas a mixed solvent. However, among the solvents described above, thenon-halogen type organic solvent is used preferably in view of theglobal environment. In this case, as the binder resin for the chargegeneration layer 215, the polycarbonate resin having the asymmetric diolingredient is used preferably.

As the blending ratio between the charge generation substance 212 andthe binder resin, it is preferred that the ratio of the chargegeneration substance 212 is within a range from 10% by weight to 99% byweight. In a case where the ratio of the charge generation substance 212is less than 10% by weight, the sensitivity is lowered. In a case wherethe ratio of the charge generation substance 212 exceeds 99% by weight,since not only the film strength of the charge generation layer 215 islowered but also the dispersibility of the charge generation substance212 is lowered to increase coarse particles to sometimes decrease thesurface charges at the portion other than the portion to be erased byexposure, this increases image defects, particularly, image foggingreferred to as “black speck” where toners are deposited to the whitebackground to form fine black spots. Accordingly, it is defined as from10% by weight to 99% by weight.

Before dispersing the charge generation substance 212 in the binderresin solution, the charge generation substance 212 may previously bepulverized by a pulverizer. The pulverizer used for pulverizationincludes, for example, a ball mill, sand mill, attritor, vibration mill,and supersonic dispersing machine.

The dispersing machine used upon dispersing the charge generationsubstance 212 into the binder resin solution includes, for example, apaint shaker, ball mill, and sand mill. As the dispersion conditions,appropriate conditions are selected so as not to cause intrusion ofimpurities due to abrasion of members constituting the container ordispersing machine to be used.

The coating method of the coating solution for charge generation layerincludes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method, and dip coating method.Among the coating method described above, since the dip coating methodis particularly excellent with various view points as described above,it has been often utilized also in a case of forming the chargegeneration layer 215. As the apparatus used for the dip coating method,a coating solution dispersing apparatus typically represented by asupersonic generation apparatus may be provided in order to stabilizethe dispersibility of the coating solution.

The film thickness of the charge generation layer 215 is, preferably,0.05 μm or more and 5 μm or less and, more preferably, 0.1 μm or moreand 1 μm or less. In a case where the film thickness of the chargegeneration layer 215 is less than 0.05 μm, the light absorptionefficiency is lowered to lower the sensitivity. In a case where the filmthickness of the generation layer 215 exceeds 5 μm, the charge transferin the charge generation layer constitutes a rate determining step inthe process of erasing charges on the surface of the photoreceptor tolower the sensitivity. Accordingly, it is defined as 0.05 μm or more and5 μm or less.

As the electroconductive material constituting the electroconductivesubstrate 211, metal materials, for example, elemental metals such asaluminum, copper, zinc, and titanium, as well as alloys such as aluminumalloys and stainless steels can be used. Further, with no particularrestriction to such metal materials, polymeric materials such aspolyethylene terephthalate, nylon, or polystyrene, hard paper or glassin which metal foils are laminated, metal materials are vapor deposited,or a layer of electroconductive compound such as electroconductivepolymer, tin oxide, or indium oxide is vapor deposited or coated on thesurface thereof can also be used. While the shape of theelectroconductive substrate 211 is cylindrical in this embodiment, it isnot restrictive but may be a circular columnar shape, sheet like shape,or endless belt shape.

The surface of the electroconductive substrate 211 may optionally beapplied with an anodizing treatment, a surface treatment with chemicalsor hot water, a coloring treatment or a random reflection treatment, forexample, by surface roughening, within a range not affecting the picturequality. In the electrophotographic process using laser as an exposuresource, since the wavelength of laser beams is coherent, the incidentlaser light and the light reflected in the photoreceptor may sometimescause interference and the interference fringe caused by interferenceappears on the images to result in image defects. Image defects by theinterference of the laser light of coherent wavelength can be preventedby applying the treatment described above to the surface of theelectroconductive substrate 211.

For improving the sensitivity and suppressing the increase of theresidual potential and fatigue in the case of repetitive use one or moreelectron accepting materials or dyes may also be added to thephotosensitive layer 214.

As the electron accepting material, electron attracting materials, forexample, acid anhydrides such as succinic acid anhydride, maleic acidanhydride, phthalic acid anhydride, and 4-chloronaphthalic acidanhydride, cyano compound such as tetraethylcyanoethylene and terephthalmalon dinitrile, aldehydes such as 4-nitrobenzoaldehyde, anthraquinonessuch as anthraquinone and 1-nitroanthraquinone, polynuclear orheterocyclic nitro compounds such as 2,4,7-trinitrofluolenone and2,4,5,7-tetranitrofluolenone, as well as diphenoquinone compounds. Thoseformed by making the electron attracting materials to higher molecularweight, etc. may also be used.

As the dyes, organic photoconductive compounds, for example, xanthenedyes, thiazine dyes, triphenylmethane dyes, quinoline pigments, andcopper phthalocyanine can be used. Such organic photoconductivecompounds function as an optical sensitizer.

A protective layer may also be disposed to the surface of thephotosensitive layer 214. Provision of the protective layer can improvethe printing resistance of the photosensitive layer 214, as well asprevent undesired chemical effects on the photosensitive layer 214caused by ozone or nitrogen oxides generated by corona discharge uponcharging the surface of the photoreceptor. For the protective layer, alayer comprising, for example, a resin, an inorganic filler-containingresin, or an inorganic oxide is used.

FIG. 18 is a schematic cross sectional view schematically showing theconstitution of an electrophotographic photoreceptor 202 according to asixth embodiment of the invention. The electrophotographic photoreceptor202 in this embodiment is similar with the electrophotographicphotoreceptor 201 of the fourth embodiment, and corresponding portionscarry identical references, for which explanation is to be omitted.

What is to be noted in the electrophotographic photoreceptor 202 isprovision of an intermediate layer 218 between the electroconductivesubstrate 211 and the photosensitive layer 214.

In a case where the intermediate layer 118 is not present between theelectroconductive substrate 211 and the photosensitive layer 214,charges are injected from the electroconductive substrate 211 to thephotosensitive layer 214 to lower the chargeability of thephotosensitive layer 214, and the surface charges in the portion otherthan the portions to be erased by exposure are decreased to sometimesresult in defects such as fogging to the images. Particularly, in a caseof forming images by using a reversal development process, since tonerimages are formed to the portion decreased with the surface charges byexposure, when the surface charges are decreased by the factor otherthan the exposure, toner is deposited to the white background to resultin fogging of images referred to as black speck in which fine blackspots are formed by the deposition of the toner on the white backgroundto remarkably deteriorate the image qualities. That is, in a case wherethe intermediate layer 218 is not present between the electroconductivesubstrate 211 and the photosensitive layer 214, this lowers thechargeability in the minute region due to the defects of theelectroconductive substrate 211 or the photosensitive layer 214 toresult in fogging of images such as black specks, which leads toremarkable image defects.

However, in the electrophotographic photoreceptor 202 in thisembodiment, since the intermediate layer 218 is provided between theelectroconductive substrate 211 and the photosensitive layer 214 asdescribed above, injection of charges from the electroconductivesubstrate 211 to the photosensitive layer 214 can be prevented.Accordingly, lowering of the chargeability of the photosensitive layer214 can be prevented to suppress the decrease of the surface charges inthe portion other than the portions to be erased by exposure andoccurrence of defects such as fogging to the images can be prevented.

Further, since the defects at the surface of the electroconductivesubstrate 211 can be covered to obtain a uniform surface by theprovision of the intermediate layer 218, the film forming property ofthe photosensitive layer 214 can be improved. Further, peeling of thephotosensitive layer 214 from the electroconductive substrate 211 can besuppressed to improve the adhesion between the electroconductivesubstrate 211 and the photosensitive layer 214.

For the intermediate layer 218, a resin layer formed of various kinds ofresin materials, or an alumite layer is used.

The resin materials forming the resin layer include, those resins suchas polyethylene resin, polypropylene resin, polystyrene resin, acrylresin, vinyl chloride resin, vinyl acetate resin, polyurethane resin,epoxy resin, polyester resin, melamine resin, silicone resin, polyvinylbutyral resin, and polyamide resin, as well as copolymer resinscontaining two or more of repetitive units constituting the resinsdescribed above. Further, casin, gelatin, polyvinyl alcohol, ethylcellulose, etc. can also be used. Among them, use of the polyamide resinis preferred and, particularly, use of alcohol soluble nylon resin ispreferred. Preferred alcohol soluble nylon resin includes, for example,so-called copolymerized nylon formed by copolymerizing 6-nylon,6,6-nylon, 6,10-nylon, 11-nylon and 2-nylon, as well as those resinformed by chemically modifying nylon such as N-alkoxymethyl modifiednylon and N-alkoxyethyl modified nylon.

The intermediate layer 218 may also contain particles such as of metaloxide. Incorporation of the particles can control the volumic resistancevalue of the intermediate layer 218 and improve the effect of preventinginjection of charges from the electroconductive substrate 211 to thephotosensitive layer 214, and can maintain the electric characteristicsof the photoreceptor under various circumstances.

The metal oxide particles include, for example, those particles oftitanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide.

In a case of incorporating particles such as of metal oxides in theintermediate layer 218, the ratio for the resin and the metal oxide(resin/metal oxide) is preferably from 90/10 to 1/99 and, morepreferably, from 70/30 to 5/95 by weight ratio.

The intermediate layer 218 can be formed, for example, by dispersing theparticles into a resin solution obtained by dissolving the resindescribed above into an appropriate solvent to prepare a coatingsolution for intermediate layer and coating the coating solution on theouter circumferential surface of the electroconductive substrate 211.

As the solvent for the resin solution, water or various kinds of organicsolvents, or a mixed solvent thereof is used. particularly, a singlesolvent such as water, methanol, ethanol, or butanol, or mixed solventcomprising such as water and alcohol, two or more kinds of alcohols,acetone or dioxolane and alcohols, and chlorine solvent such asdichloroethane, chloroform, or trichloroethane and alcohols are usedsuitably.

As the method of dispersing the particles in the resin solution, ageneral method of using a ball mill, sand mill, attritor, vibrationmill, or supersonic dispersing machine, etc. can be used.

The coating method of the coating solution for intermediate layerincludes, for example, a spraying method, a bar coating method, a rollcoating method, a blade method, wringing method, and a dip coatingmethod. Particularly, since the dip coating method is relatively simpleand is excellent in view of the productivity and the cost, it has beenoften utilized also in a case of forming the intermediate layer 218.

The film thickness of the intermediate layer 218 is, preferably, from0.01 μm or more to 20 μm or less and, preferably, 0.05 μm or more to 10μm or less. In a case where the film thickness of the intermediate layer218 is less than 0.01 μm, it no more substantially functions as theintermediate layer 218 and no uniform surface property by coating thedefects of the surface of the electroconductive substrate 211 can beobtained, and injection of charges from the electroconductive substrate211 to the photosensitive layer 214 can not be prevented to lower thechargeability of the photosensitive layer 214. It is not preferred toincrease the film thickness of the intermediate layer 218 to more than20 μm since formation of the intermediate layer 18 is difficult and thephotosensitive layer 214 can not be formed uniformly on the outercircumferential surface of the intermediate layer 218 to lowersensitivity of the photoreceptor in a case of forming the intermediatelayer 218 by the dip coating method.

Further, various additives such as an antioxidant a sensitizer and aUV-absorber may be added optionally to each of the layers of thephotosensitive layer in the fifth embodiment and the sixth embodimentdescribed above. This can improve potential characteristics. Further,the stability of the coating solution upon forming the layer by coatingis improved. Further, this can mitigate the fatigue deterioration toimprove the durability upon repetitive use of the photoreceptor.

Particularly preferred antioxidant includes, for example, phenolcompounds, hydroquinone compounds, tocopherol compounds and aminecompounds. The antioxidant is preferably used within a range from 0.1%by weight or more and 50% by weight or less based on the chargetransportation substance 213. In a case where the amount of theantioxidant to be used is less than 0.1% by weight, no sufficient effectcan be obtained for the improvement of the stability of the coatingsolution and the durability of the photoreceptor. In a case where theamount of the antioxidant to be used exceeds 50% by weight, it gives anundesired effect on the characteristic of the photoreceptor.Accordingly, it is defined as 0.1% by weight or more and 50% by weightor less.

Further, while the photosensitive layer 214 disposed to theelectrophotogrphic photoreceptor of the fifth embodiment or the sixthembodiment described above is a stacked type photosensitive layer havinga stacked structure of the charge generation layer 215 containing thecharge generation substance 212 and the charge transportation layer 216containing the charge transportation substance 213 and the binder resin217, this is not limited thereto but may also be a single-layered typephotosensitive layer having a single layer containing the chargegeneration martial 212, the charge transportation substance 213containing the enamine compound represented by the general formula (2)and the binder resin 217 containing the polycarbonate resin having theasymmetric diol ingredient.

As the image forming apparatus according to a seventh embodiment of theinvention, an image forming apparatus 300 having the electrophotographicphotoreceptor 201 (photoreceptor 201) of the fourth embodiment describedabove is to be exemplified. The image forming apparatus according to theinvention is not restricted to the content of the followingdescriptions.

FIG. 19 is a view for side elevation arrangement schematically showingthe constitution of the image forming apparatus 300.

The image forming apparatus 300 comprises a photoreceptor 201rotationally supported on not illustrated image forming apparatus mainbody, and driving means not illustrated for rotationally driving thephotoreceptor 201 around a rotational axis 244 in the direction of anarrow 241. The not illustrated driving means comprises, for example, amotor as a power source and rotationally drives the photoreceptor 201 ata predetermined circumferential speed by transmitting the power from themotor by way of not illustrated gears to a substrate constituting thecore of the photoreceptor 201.

At the periphery of the photoreceptor 201, are disposed a charger 232,not-illustrated exposure means, a developing device 233, a transfercharger 234 and a cleaner 236 in this order from the upstream to thedownstream in the rotational direction of the photoreceptor 201 shown bythe arrow 241. The cleaner 236 is disposed together with a notillustrated charge eliminator.

The charger 232 is the charging means for charging the outercircumferential surface 243 of the photoreceptor 201 to a predeterminedpotential. The charger 232 is a contact type charging means such as aroller charging system.

The exposure means comprise, for example, a semiconductor laser as alight source and irradiate a light 231 such as a laser beam outputtedfrom the light source to the outer circumferential surface 243 of thephotoreceptor 201 situated between the charger 232 and the developingdevice 233 thereby subjecting the charged outer circumferential surface243 of the photoreceptor 201 to exposure to light in accordance withimage information.

The developing device 233 is developing means for developingelectrostatic latent images formed by exposure to the outercircumferential surface 243 of the photoreceptor 201 by a developer andcomprise a developing roller 233 a opposed to the photoreceptor 201 andsupplying a toner to the outer circumferential surface 243 of thephotoreceptor 201 and a casing 233 b for rotationally supporting thedeveloping roller 233 a around a rotational axis parallel with therotational axis 244 of the photoreceptor 201 and housing the developercontaining the toner to the inner space thereof.

The transfer charger 234 is transferring means for transferring thetoner images formed on the outer circumferential surface 243 of thephotoreceptor 201 by applying charges at the polarity opposite to thetoner on the transfer paper 251 supplied between the photoreceptor 201and the transfer charger 234 by not illustrated transferring means inthe direction of the arrow 242.

The cleaner 236 is cleaning means for removing to recover the tonerremaining on the outer circumferential surface 243 of the photoreceptor201 after the transferring operation by the transfer charger 234 andcomprises a cleaning blade 236 a for separating the toner remaining onthe outer circumferential surface 243 of the photoreceptor 201 from theouter circumferential surface 243, and a recovery casing 236 b forhousing the toner peeled by the cleaning blade 236 a.

Further, a fixing device 235 as fixing means for fixing transferredimages is disposed in the direction where the transfer paper 251 isconveyed after passage between the photoreceptor 201 and the transfercharger 234. The fixing device 235 comprises a heating roller 235 ahaving heating means not illustrated and a press roller 235 b opposed tothe heating roller 235 a and pressed by the heating roller 235 a to forma contact portion.

The image forming operation by the image forming apparatus 300 is to bedescribed. At first, when the photoreceptor 201 is driven rotationallyby the driving means in the direction of the arrow 241, the outercircumferential surface 243 of the photoreceptor 201 is uniformlycharged to a predetermined positive or negative potential by the charger232 disposed upstream to the focusing point of the light 231 from theexposure means in the rotational direction of the photoreceptor 201.Then, the light 231 is irradiated from the exposure means to the outercircumferential surface 243 of the photoreceptor 201. The light 231 fromthe light source is scanned repetitively in the longitudinal directionof the photoreceptor 201 which is a main scanning direction. When thephotoreceptor 201 is rotated and the light 231 from the light source isrepetitively scanned, exposure in accordance with image information isapplied to the outer circumferential surface 243 of the photoreceptor201. By the exposure, surface charges at the portion irradiated with thelight 231 are eliminated to result a difference between the surfacepotential at the portion irradiated with the light 231 and the surfacepotential at the portion not irradiated with the light 231, to formelectrostatic latent images to the outer circumferential surface 243 ofthe photoreceptor 201. Then, a toner is supplied to the outercircumferential surface 243 of the photoreceptor 201 formed with theelectrostatic latent images from the developing roller 233 a of thedeveloping device 233 located downstream to the focusing point of thelight 231 from the light source in the rotationally direction of thephotoreceptor 201 to develop the electrostatic latent images, and tonerimages are formed to the outer circumferential surface 243 of thephotoreceptor 201.

Further, in synchronization with exposure to the photoreceptor 201,transfer paper 251 is fed by the conveying means in the direction of thearrow 242 between the photoreceptor 201 and the transfer roller 234located downstream to the developing device 233 in the rotationaldirection of the photoreceptor 201.

When the transfer paper 251 is fed between the photoreceptor 201 and thetransfer charger 234, the transfer charger 234 gives charges at thepolarity opposite to that of the toner to the transfer paper 251. Thus,the toner images formed on the outer circumferential surface 243 of thephotoreceptor 201 are transferred onto the transfer paper 251.

The transfer paper 251 transferred with the toner images are conveyed byconveying means to the fixing device 235 and heated and pressed uponpassage through the contact portion between the heating roller 235 a andthe press roller 235 b of the fixing device 235. Thus, the toner imageson the transfer paper 251 are fixed to the transfer paper 251 as firmimages. The transfer paper 251 thus formed with the images aredischarged by the conveying means to the outside of the imaging formingapparatus 300.

On the other hand, a toner remaining on the outer circumferentialsurface 243 of the photoreceptor 201 after the transferring operation bythe transfer charger 234 is peeled from the outer circumferentialsurface 243 of the photoreceptor 201 by the cleaning blade 236 a of thecleaner 236 located downstream to the transfer charger 234 in therotational direction of the photoreceptor 201 and upstream to thecharger 232 in the rotational direction and recovered in the recoverycasing 236 b. Electric charges on the outer circumferential surface 243of the photoreceptor 201 removed with the toner are eliminated by acharge eliminator, and the electrostatic latent images on the outercircumferential surface 243 of the photoreceptor 201 are erased. Then,the photoreceptor 201 is further rotated and a series of operationsstarting from charging for the photoreceptor 1 are repeated again. Asdescribed above, images are formed continuously.

Since the photoreceptor 201 provided to the image forming apparatus 300has the photosensitive layer 214 containing the polycarbonate resinhaving the asymmetric diol ingredient and the enamine compoundrepresented by the general formula (2) as described above, it has highcharge potential and charge retainability, high sensitivity andsufficient light responsivity, as well as excellent durability andcharacteristics thereof are not deteriorated even in a case of use undera low temperature circumstance or in a high speed electrophotographicprocess. Accordingly, an image forming apparatus of high reliabilitycapable of providing high quality images over a long period of timeunder various circumstances can be obtained. Further, since thecharacteristics of the photoreceptor 201 are not deteriorated even bylight exposure, deterioration of image quality due to exposure of thephotoreceptor to light for example during maintenance can be preventedand reliability of the image forming apparatus can be improved.

As has been described above, while the imaging forming apparatus 300 ofthis embodiment has the electrophotographic photoreceptor 201 of thefilm embodiment but this is not limitative but it may be provided withthe electrophotographic photoreceptor 202 of the sixth embodiment.

Further, while the charger 232 is contact type charging means but it isnot restricted thereto and may also be non-contact type charging meanssuch as a corona charging system.

Example 10

After adding 9 parts by weight of dendritic titanium oxide applied witha surface treatment with aluminum oxide (chemical formula: Al₂O₃) andzirconium dioxide (chemical formula: ZrO₂) (manufactured by IshiharaSangyo Co.: TTO-D-1), and 9 parts by weight of copolymerized nylon resin(manufactured by Toray Co.: Amilan CM8000) to a mixed solvent of 41parts by weight of 1,3-dioxolane and 41 parts by weight of methanol,they were dispersed for 8 hours by a paint shaker to prepare a coatingsolution for intermediate layer. The coating solution for intermediatelayer was dipped in a coating tank and, after dipping a cylindricalelectroconductive substrate 211 made of aluminum of 65 mm diameter and334 mm entire length into the coating tank, and then pulling uptherefrom, an intermediate layer 218 of 1.0 μm film thickness was formedon the outer circumferential surface of the electroconductive substrate211.

Then, 2 parts by weight of oxotitanium phthalocyanine having a crystalstructure showing a distinct diffraction peak at least at a Bragg angle(2θ±0.2°) of 27.2° in X-ray diffraction spectrum by Cu—Kα characteristicX-rays (wavelength: 1.54 Å) as oxotitanium phthalocyanine for the chargegeneration substance 212, one part by weight of a polyvinyl butyralresin (manufactured by Sekisui Chemical Industry Co.: S-leck BM-S), and97 parts by weight of methyl ethyl ketone were mixed, and dispersed by apaint shaker to prepare a coating solution for charge generation layer.By coating the coating solution for charge generation layer on the outercircumferential surface of the previously formed intermediate layer 218by the same dip coating method as in the intermediate layer 218, acharge generation layer 215 of 0.4 μm thickness was formed on the outercircumferential surface of the intermediate layer 218.

Then, 10 parts by weight of the enamine compound of Exemplified CompoundNo. 1 shown in Table 6, 10 parts by weight of the polycarbonate resinhaving the structural unit containing the asymmetric diol ingredientrepresented by the structural formula (22-3) shown in Table 40 as abinder resin 217 (viscosity average molecular weight: 40,000), one partby weight of 2,6-di-t-butyl-4-methylphenol, and 0.01 parts by weight ofdimethyl polysiloxane (manufactured by Shinetsu Chemical Industry Co.:KF-96) were dissolved in 80 parts by weight of tetrahydrofuran toprepare a coating solution for charge transportation layer. Aftercoating the coating solution for charge transportation layer by the samedip coating method as for the intermediate layer 218 formed previouslyonto the outer circumferential surface of the charge generation layer215 formed previously, it was dried at 130° C. for one hour to prepare acharge transportation layer 216 of 30 μm thickness.

As described above, the electrophotographic photoreceptor of theconstitution shown in FIG. 18 satisfying the conditions of the inventionwas prepared.

Examples 11 to 14

Four kinds of electrophotographic photoreceptors satisfying theconditions of the invention were prepared in the same manner as inExample 10 except for changing the amount of the polycarbonate resinhaving the structural unit containing the asymmetric diol ingredientrepresented by the structural formula (22-3) as the binder resin 217 forthe charge transportation layer 216 to 12 parts by weight, 18 parts byweight, 30 parts by weight or 40 parts by weight. However, the amount oftetrahydrofuran in the coating solution for each charge transportationlayer was controlled such that the solid concentration of the coatingsolution for charge transportation layer was 20% by weight.

The viscosity of the coating solution for charge transportation layerwas increased extremely in Example 14 where the amount of thepolycarbonate resin having the structural unit containing the asymmetricdiol ingredient represented by the structural formula (22-3) was changedto 40 parts by weight.

Examples 15 to 19

Five kinds of electrophotographic photoreceptors satisfying theconditions of the invention were prepared in the same manner as inExample 10 except for using the enamine compound of Exemplified CompoundNo. 61 shown in Table 14 instead of Exemplified Compound No. 1 as thecharge transportation substance 213 and using 10 parts by weight, 12parts by weight, 18 parts by weight, 30 parts by weight or 40 parts byweight of the polycarbonate resin having the structural unit containingthe asymmetric diol ingredient represented by the structural formula(22-5) shown in Table 40 (viscosity average molecular weight: 40,000) asthe binder resin 217 of the charge transportation layer 216 instead ofthe polycarbonate resin having the structural unit containing theasymmetric diol ingredient represented by the structural formula (22-3).However, the amount of tetrahydrofuran in the coating solution for eachcharge transportation layer was controlled such that the solidconcentration of the coating solution for charge transportation layerwas 20% by weight.

The viscosity of the coating solution for charge transportation layerwas increased extremely in Example 19 where the amount of thepolycarbonate resin having the structural unit containing the asymmetricdiol ingredient represented by the structural formula (22-5) was changedto 40 parts by weight.

Example 20

An electrophotographic photoreceptor satisfying the conditions of theinvention was prepared in the same manner as in Example 10 except forusing, instead of the polycarbonate resin having the structural unitcontaining the asymmetric diol ingredient represented by the structuralformula (22-3), 18 parts by weight of a copolymerized polycarbonateresin having the structural unit containing the asymmetric diolingredient represented by the structural formula (22-3) and thestructural unit containing the siloxane structure represented by thefollowing structural formula (24) (viscosity average molecular weight:40,000) as the binder resin 217 of the charge transportation layer 216.However, the amount of tetrahydrofuran in the coating solution forcharge transportation layer was controlled such that the solidconcentration in the coating solution for charge transportation layerwas 20% by weight.

Comparative Examples 5 to 9

Five kinds of electrophotographic photoreceptors not satisfying theconditions of the invention were manufactured in the same manner as inExample 10 except for using, instead of a polycarbonate resin having thestructural unit containing the asymmetrical diol ingredient representedby structural formula (22-3), 10 parts by weight, 12 parts by weight, 18parts by weight, 30 parts by weight, or 40 parts by weight of bisphenolA polycarbonate resin having the structural unit containing the diolingredient derived from bisphenol A represented by the followingstructural formula (A-1) (viscosity average molecular weight: 40,000) asthe binder resin 217 of a charge transportation layer 216.

However, in Comparative Example 8 in which the amount of the bisphenol Apolycarbonate resin was 30 parts by weight and in Comparative Example 9in which it was 40 part by weight, a portion of the bisphenol Apolycarbonate resin was not dissolved and the coating solution forcharge transportation layer was gelled upon preparation of the coatingsolution for charge transportation layer, and the photoreceptor couldnot be prepared.

Further, in Comparative Example 5 where the amount of the bisphenol Apolycarbonate resin was set to 10 parts by weight and in ComparativeExample 6 where it was set to 12 parts by weight and in ComparativeExample 7 where it was set to 18 parts by weight, although thephotoreceptors could be prepared, the coating solution for chargetransportation layer to be used was gelled in several days after thepreparation.

Comparative Example 10

An electrophotographic photoreceptor not satisfying the conditions ofthe invention was manufactured in the same manner as in Example 10except for using the Comparative Compound A represented by the followingstructural formula (25) instead of the Exemplified Compound 1 as thecharge transportation substance 213, and changing the amount of thepolycarbonate resin having the structural unit containing the asymmetricdiol ingredient represented by the structural formula (22-3) as thebinder resin 217 of the charge transportation layer 216 to 18 parts byweight. However, the amount of the tetrahydrofuran in the coatingsolution for charge transportation layer was controlled such that thesolid concentration in the coating solution for charge transportationlayer was 20% by weight.

Comparative Example 11

An electrophotographic photoreceptor not satisfying the conditions ofthe invention was manufactured in the same manner as in Example 10except for using the Comparative Compound B represented by the followingstructural formula (26) instead of the Exemplified Compound 1 as thecharge transportation substance 213, and changing the amount of thepolycarbonate resin having the structural unit containing the asymmetricdiol ingredient represented by the structural formula (22-3) as thebinder resin 217 of the charge transportation layer 216 to 18 parts byweight. However, the amount of the tetrahydrofuran in the coatingsolution for charge transportation layer was controlled such that thesolid concentration in the coating solution for charge transportationlayer was 20% by weight.

Comparative Example 12

An electrophotographic photoreceptor not satisfying the conditions ofthe invention was manufactured in the same manner as in Example 10except for using the enamine compound represented by the structuralformula (27) (hereinafter referred to as “Comparative Compound C”)instead of the Exemplified Compound 1 as the charge transportationsubstance 213, and changing the amount of the polycarbonate resin havingthe structural unit containing the asymmetric diol ingredientrepresented by the structural formula (22-3) as the binder resin 217 ofthe charge transportation layer 216 to 18 parts by weight. However, theamount of the tetrahydrofuran in the coating solution for chargetransportation layer was controlled such that the solid concentration inthe coating solution for charge transportation layer was 20% by weight.

Evaluation 1

Printing resistance and stability of electric characteristics wereevaluated for each of the electrophotographic photoreceptors prepared inExamples 10 to 20 and Comparative Examples 5 to 7, and 10 to 12described above. Evaluation was conducted as described below.

(Printing Resistance)

Each of the electrophotographic photoreceptors prepared in Examples 10to 20 and Comparative Examples 5 to 7, and 10 to 12 was mounted to adigital copying machine (manufactured by Sharp Corp: AR-S507) set at acopying speed of 50 sheets of Japanese Industrial Standards (JIS) A4size paper per min, respectively. After conducting image formation for300,000 sheets, the film thickness d1 of the photosensitive layer wasmeasured, and a difference between the value and the film thickness d0of the photosensitive layer after preparation was determined as a filmreduction amount Δd (=d0−d1), which was used as the evaluation index fora printing resistance. It was evaluated as excellent (⊙) in a case wherethe film reduction amount Δd was 10 μm or less, evaluated as good (◯) ina case where the film reduction amount Δd was more than 10 μm and 16 μmor less, evaluated as ordinary (Δ) in a case where the film reductionamount Δd was more than 16 μm and 20 μm or less, and evaluated as poor(x) in a case where the film reduction amount Δd was more than 20 μm. Ina copying machine mounting the photoreceptor of Comparative Example 5,since the film reduction of the photosensitive layer was excessivelylarge and image formation can not be conducted up the specified numberof sheets (300,000), it was evaluated as poor (x).

(Stability of Electric Characteristics)

Each of electrophotographic photoreceptors prepared in Examples 10 to 20and Comparative Examples 5 to 7, and 10 to 12 was mounted respectivelyto a digital copying machine (manufactured by Sharp Corp.: AR-S508) inwhich a surface potential meter (manufactured by Treck: Model 347) wasdisposed to the inside such that the surface potential of thephotoreceptor in the image forming process could be measured, and thesurface of the photoreceptor was charged by applying a voltage atnegative (−) 6 kV to the photoreceptor under a normal temperature/normalhumidity circumstance (hereinafter referred to as “N/N circumstance”) ata temperature of 22° C. and at a relative humidity of 65% (22° C./65%RH), and the surface potential of the photoreceptor just after chargingwas measured as a charge potential V₀ (V). Then, exposure was applied byusing a laser light to the charged surface of the photoreceptor, and thesurface potential of the photoreceptor just after-exposure was measuredas the after-exposure potential V_(L)(V).

Further, the after-exposure potential V_(L) as the surface potential ofthe photoreceptor just after being subjected to exposure to a laserlight was measured under a low temperature/low humidity circumstance(hereinafter referred as “L/L circumstance”) at a temperature of 5° C.and at a relative humidity of 20% (5° C./20% RH) in the same manner asthat under the N/N circumstance.

The difference between the absolute value for V_(L)(1) and the absolutevalue V_(L)(2) assuming the after-exposure potential V_(L) measuredunder the N/N circumstance as V_(L)(1) and the after-exposure potentialV_(L) measured under L/L circumstance as V_(L)(2) was determined as apotential fluctuation ΔV_(L) (=|V_(L)(2)|−|V_(L)(1) |), which was usedas the index for the evaluation of the stability for the electriccharacteristics. The potential fluctuation ΔV_(L) shows that as thevalue is larger, the difference between the after-exposure potentialV_(L)(2) under the L/L circumstance and the difference potential islarger compared with the potential difference between the after-exposurepotential V_(L)(1) under the N/N circumstance and the referencepotential, that is, the light responsivity under the L/L circumstance islowered compared with that under the N/N circumstance. Accordingly, itwas evaluated as good (◯) in a case where the value for the potentialfluctuation ΔV_(L) was lower than 110 V, as ordinary (Δ) in a case wherethe value for the potential fluctuation ΔV_(L) was 110 V or higher andlower than 130 V, and as poor (x) in a case where the value for thepotential fluctuation ΔV_(L) was 130 V or higher.

Evaluation 2

The state of coating solutions for charge transportation layer usedrespectively in Examples 10 to 20 and Comparative Examples 5 to 12 wasevaluated and used as the evaluation index for the aging stability ofthe coating solution for charge transportation layer. It was evaluatedas good (◯) in a case where the coating solution for chargetransportation layer had a viscosity suitable to dip coating and was notgelled even lapse of several days from preparation, evaluated asordinary (Δ) in a case where the coating solution for chargetransportation layer had a high viscosity but was not gelled, andevaluated as poor (x) in a case where the coating solution for chargetransportation layer was gelled.

Table 44 shows the result of evaluations. In Table 44, the polycarbonateresins used for the binder resin 217 are shown by the numbers ofstructural formulae showing the structural units thereof.

TABLE 44 Printing Charge resistance Stability for electrictransportation layer Film characteristics Aging stability Chargereduction N/N electric L/L poten- State of Photo- transportation Binderamount Eval- characteristic tial flu Eval- coating Eval- receptorsubstance (A) resin (B) A/B Δ d(μm) uation V₀(V) V_(L) (V) ΔV_(L)(V)uation solution uation Remarks Example 10 Exemplified Structural 10/1020 Δ −628 −20 70 ◯ ◯ Compound 1 formula (22-3) Example 11 ExemplifiedStructural 10/12 16 ◯ −624 −23 80 ◯ ◯ Compound 1 formula (22-3) Example12 Exemplified Structural 10/18 14 ◯ −629 −30 90 ◯ ◯ Compound 1 formula(22-3) Example 13 Exemplified Structural 10/30 10 ⊙ −618 −40 100 ◯ ◯Compound 1 formula (22-3) Example 14 Exemplified Structural 10/40 8 ⊙−624 −50 120 Δ high Δ Compound 1 formula viscosity (22-3) Example 15Exemplified Structural 10/10 18 Δ −624 −15 60 ◯ ◯ Compound 61 formula(22-5) Example 16 Exemplified Structural 10/12 14 ◯ −626 −17 68 ◯ ◯Compound 61 formula (22-5) Example 17 Exemplified Structural 10/18 12 ◯−619 −23 79 ◯ ◯ Compound 61 formula (22-5) Example 18 ExemplifiedStructural 10/30 9 ⊙ −624 −28 90 ◯ ◯ Compound 61 formula (22-5) Example19 Exemplified Structural 10/40 6 ⊙ −617 −35 113 Δ high Δ Compound 61formula viscosity (22-5) Example 20 Exemplified Structural 10/18 13 ◯−618 −25 88 ◯ ◯ Compound 61 formula (22-3) + Structural formula (24)Comp. Ex. 5 Exemplified Structural 10/10 — X −621 −21 75 ◯ gelled in XCompound 1 formula several (A) days Comp. Ex. 6 Exemplified Structural10/12 20 Δ −629 −25 88 ◯ gelled in X Compound 1 formula several (A) daysComp. Ex. 7 Exemplified Structural 10/18 17 Δ −625 −33 97 ◯ gelled in XCompound 1 formula several (A) days Comp. Ex. 8 Exemplified Structural10/30 — — — — — — partially X Photo- Compound 1 formula not receptor (A)dissolved could but gelled not be prepared Comp. Ex. 9 ExemplifiedStructural 10/40 — — — — — — partially X Photo- Compound 1 formula notreceptor (A) dissolved could but gelled not be prepared Comp. Ex. 10Comp. Structural 10/18 14 ◯ −620 −80 140 X ◯ compound A formula (22-3)Comp. Ex. 11 Comp. Structural 10/18 15 ◯ −619 −100 150 X ◯ compound Bformula (22-3) Comp. Ex. 12 Comp. Structural 10/18 14 ◯ −623 −95 138 X ◯compound C formula (22-3)

From the comparison between Examples 10 to 20 and Comparative Examples 5to 9, it was found that, in a case of using tetrahydrofuran as annon-halogen type organic solvent for the solvent, while the coatingsolution for charge transportation layer gelled in Comparative Examples5 to 9 using a bisphenol A polycarbonate resin as the binder resin 217for the charge transportation layer 216, the coating solution for chargetransportation layer was not gelled but stable in Examples 10 to 20using the polycarbonate resin having the asymmetric diol ingredient.

Further, from the comparison between Examples 11 and 16 and ComparativeExample 6 and the comparison between Examples 12 and 17 and ComparativeExample 7, it was found that the photoreceptors of Examples 11, 12, 16,and 17 using the polycarbonate resin having the asymmetric diolingredient as the binder resin 17 for the charge transportation layer216 showed less film reduction amount Δd of the photosensitive layer andwere excellent in the printing resistance compared with thephotoreceptors of Comparative Examples 6, and 7 using the bisphenol Apolycarbonate resin.

Further, from the comparison between Examples 12, 17, and 20 andComparative Examples 10 to 12, the photoreceptors of Examples 12, 17,and 20 using the enamine compound represented by the general formula (2)for the charge transportation substance 213, different from thephotoreceptor of Comparative Example 10 using the Comparative CompoundA, the photoreceptor of Comparative Example 11 using the ComparativeCompound B, and the light sensitive of Comparative Example 12 using theComparative Compound C, showed smaller potential difference between theafter-exposure potential V_(L) under the N/N circumstance and referencepotential and had excellent light responsivity even in a case where theratio A/B for the charge transportation substance 213 (A) and binderresin 217 (B) in the charge transportation layer 216 was defined as10/18 by weight ratio and the binder resin 217 was added at a highratio. Further, it was found that the value of the potential fluctuationΔV_(L) was small and it had a sufficient light responsivity also underthe L/L circumstance.

Further, from the comparison between Example 10 and Examples 11 to 14and comparison between Example 15 and Examples 16 to 19, it was foundthat the photoreceptors of Examples 10 and 15 in which the ratio A/B was10/10 by weight ratio that exceeds 10/12, and the ratio of the binderresin was lowered had larger film reduction amount Δd and were poor inthe printing resistance compared with the photoreceptors of Examples 11to 14 and Examples 16 to 19 with the ratio A/B being 10/12 or less.

Further, from the comparison between Examples 10 to 13 and Example 14,and comparison between Examples 15 to 18 and Example 19, it was foundthat the photoreceptors of Examples 14 and 19 in which the ratio A/B was10/40 was below 10/30 and the ratio of the binder resin was highershowed smaller film reduction amount Δd and were excellent in theprinting resistance compared with the photoreceptors of Examples 10 to13 and Examples 15 to 18 in which the ratio A/B was 10/30 or more, butthey showed larger value for potential fluctuation ΔV_(L) and were poorin the light responsivity under the L/L circumstance. Further, since theviscosity of the coating solution for charge transportation layer wasextremely high in Examples 14 and 19, the productivity was low and theuniformness of the formed charge transportation layer 216 was worsened,and a number of image failure due to local unevenness of the filmthickness was formed in the images formed by the copying machinemounting the photoreceptors described above.

Further, from the comparison between Example 20 and Example 12, it wasfound that the photoreceptor of Example 20 using the polycarbonate resinhaving the asymmetrical diol ingredient and the siloxane structure inthe binder resin 217 of the charge transportation layer 216 had smallerfilm reduction amount Δd and was excellent in the printing resistancecompared with the photoreceptor of the Example 12 using thepolycarbonate resin not having the siloxane structure. Further, thesurface of the photoreceptor of Example 20 suffered from less injurieseven after formation of images by 300,000 sheets and image defects dueto cleaning failure were not observed in the images formed by thecopying machine mounting the photoreceptor of Example 20.

As described above, by incorporating the enamine compound represented bythe general formula (2), and the polycarbonate resin having theasymmetric diol ingredient in combination to the photosensitive layer asdescribed above, it is possible to obtain an electrophotographicphotoreceptor having high charge potential, high sensitivity andsufficient light responsivity, as well as excellent in durability, withno deterioration for the characteristics thereof even in a case of useunder the low temperature circumstance, and having high reliability andpreferred productivity. Further, the printing resistance of thephotosensitive layer could be improved without lowering the lightresponsivity by defining the ratio A/B for the charge transportationsubstance (A) and the binder resin (B) as 10/12 to 10/30 by weightratio.

FIG. 20 is a side elevational view for the arrangement schematicallyshowing the constitution of an image forming apparatus 301 according toan eighth embodiment of the invention and FIG. 21 is a viewschematically showing the constitution of an electrophotographicphotoreceptor 310 provided to the image forming apparatus 301 shown inFIG. 20. At first, an electrophotographic photoreceptor 310 (hereinafteralso referred to simply as “photoreceptor”) as a characteristic memberfor the image forming apparatus 301 of the invention is to be describedwith reference to FIG. 21.

FIG. 21A is a perspective view schematically showing the constitution ofa photoreceptor 310. FIG. 21B is a fragmentary cross sectional viewschematically showing the constitution of the photoreceptor 310. Thephotoreceptor 310 comprises a cylindrical electroconductive substrate311 formed of an electroconductive material and a photosensitive layer314 disposed on the outer circumferential surface of theelectroconductive substrate 311. The photosensitive layer 314 has astacked structure in which a charge generation layer 315 containing acharge generation substance 312 that generates charges by absorption oflight and a charge transportation layer 316 containing a chargetransportation substance 313 having an ability of accepting andtransferring charges generated in the charge generation substance 312and a binder resin 317 for binding the charge transportation substance313 are stacked in this order on the outer circumferential surface ofthe electroconductive substrate 311. That is, the photoreceptor 310 is astacked type photoreceptor.

The photosensitive layer 314 contains the enamine compound representedby the general formula (2) as the charge transportation substance 313:

[Ka 42]

Since the enamine compound represented by the general formula (2)contained in the photosensitive layer 314 as the charge transportationsubstance 313 has a high charge mobility, it is possible to obtain aphotoreceptor 310 having high chargeability, sensitivity, andresponsivity, with no deterioration of the electric characteristics evenin a case of repetitive use.

Further, since the enamine compound represented by the general formula(2) is excellent in the compatibility with the binder resin 317 and thesolubility to a solvent, it is dispersed uniformly with no agglomerationin the binder resin 317, and dissolved uniformly with no agglomerationin the coating solution upon forming the charge transportation layer 316by coating as will be described later. Accordingly, the photoreceptor310 has a uniform charge transportation layer 316 with scarce defectssuch as a portion where the charge transportation substance 313 isagglomerated.

That is, by the use of the enamine compound represented by the generalformula (2) as the charge transportation substance 313, as describedabove, it is possible to obtain a photoreceptor 310 having highchargeability, sensitivity, and responsivity, with no deterioration ofthe electric characteristics even in a case of repetitive use and withscarce defects in the charge transportation layer 316. Further, it ispossible to improve the stability of the coating solution upon formingthe charge transportation layer 316 by coating to improve the productionefficiency of the photoreceptor 310.

As the charge transportation substance 313, the enamine compoundrepresented by the general formula (3) is used suitably among theenamine compounds represented by the general formula (2):

Since the enamine compound represented by the general formula (3) has aparticularly high charge mobility among the enamine compoundsrepresented by the general formula (2), an photoreceptor 310 havingfurther higher sensitivity and responsivity can be obtained by using theenamine compound represented by the general formula (3) as the chargetransportation substance 313. Accordingly, it is possible to obtain animage forming apparatus 301 of high reliability capable of providingimages at high quality also in a case of forming images at a high speed.

Further, since the enamine compound represented by the general formula(3) can be synthesized relatively easily at a high yield and produced ata reduced cost among the enamine compounds represented by the generalformula (2), the photoreceptor 310 having the excellent characteristicsas described above can be produced at a reduced manufacturing cost.Accordingly, the manufacturing cost for the image forming apparatus 301can be decreased.

Further, among the enamine compounds represented by the general formula(2), a particularly excellent compound with a view point of thecharacteristics, cost and productivity includes, in the same manner asdescribed above, those in which both of Ar¹ and Ar² are phenyl group,Ar³ is a phenyl group, tolyl group, p-methoxyphenyl group, biphenylylgroup, naphthyl group or thienyl group, at least one of Ar⁴ and Ar⁵ is aphenyl group, p-tolyl group, p-methoxyphenyl group, naphthyl group,thienyl group, or thiazolyl group, and each of R¹¹, R¹², R¹³, and R¹⁴ isa hydrogen atom, and n is 1.

The enamine compound represented by the general formula (2) can beproduced in the same manner as described above.

As the enamine compound represented by the general formula (2), those,for example, selected from the group consisting of the exemplifiedcompounds shown in Table 6 to Table 37 described above are used eachalone or as a mixture of two or more of them.

The enamine compound represented by the general formula (2) may be usedalso in admixture with the same other charge transportation substance asdescribed previously for the charge transportation substance 313.Further, polymers having the groups derived from the compounds in themain chain or the side chain, for example, poly-(N-vinylcarbazole),poly-(1-vinylpyrene), and poly-(9-vinylanthracene) can also bementioned.

In a case of using the enamine compound represented by the generalformula (2) in admixture with other charge transportation substance asdescribed above, since the charge transportation substance 313 maysometimes cause agglomeration to form a number of defects in the chargetransportation layer 316 in a case where the ratio of other chargetransportation substance is excessive, it is preferred to use a mixturein which the enamine compound represented by the general formula (2) iscontained as a main ingredient as the charge transportation substance313.

The charge transportation layer 316 is formed in a manner where thecharge transportation substance 313 containing the enamine compoundrepresented by the general formula (2) is bonded to the binder resin317. Specific examples of the resin used for the binder resin 317include, for example, vinyl polymer resins such as a polymethylmethacrylate resin, polystyrene resin, and polyvinyl chloride resin,copolymer resins containing two or more of repetitive units constitutingthem, polyarylate resin, polycarbonate resin, polyester resin, polyestercarbonate resin, polysulfone resin, phenoxy resin, epoxy resin, siliconeresin, polyamide resin, polyether resin, polyurethane resin,polyacrylamide resin, and phenol resin. Further, they also includethermosetting resins formed by partially crosslinking the resinsdescribed above. The resins may be used each alone or may be used as amixture of two or more of them.

In the charge transportation layer 316, the ratio A/B for the weight Aof the enamine compound represented by the general formula (2) containedas the charge transportation substance 313 and the weight B for thebinder resin 317 is preferably from 10/12 to 10/30. By defining theratio A/B to 10/12 to 10/30 and incorporating the binder resin 317 at ahigh ratio in the charge transportation layer 316, a photoreceptor 310providing a tough photosensitive layer 314 and excellent durability canbe obtained.

On the other hand, in a case where the ratio of the binder resin 317 isincreased with the ratio A/B being 10/12 or less, the ratio of theenamine compound represented by the general formula (2) as the chargetransportation substance 313 is lowered as a result. In a case of usingthe known charge transportation substance for the charge transportationsubstance 313 and defining the ratio between the weight of the chargetransportation substance 313 and the weight of the binder resin 317(charge transportation substance 313/binder resin 317) to 10/12 or less,the sensitivity and the responsivity become insufficient to sometimescause image defects. However, since the enamine compound represented bythe general formula (2) has a high charge mobility, even when the ratioof the enamine compound represented by the general formula (2) islowered with the A/B being 10/12 or less, the photoreceptor 310 hassufficiently high sensitivity and responsivity and images at highquality can be provided.

Accordingly, by defining the ratio A/B as from 10/12 to 10/30, it ispossible to attain a photoreceptor 310 having high sensitivity andresponsivity and excellent in the durability and to obtain an imageforming apparatus 301 capable of providing images at high quality for alonger period of time.

In a case where the ratio A/B exceeds 10/12 and the ratio of the binderresin 317 is excessively low, the wear amount of the photosensitivelayer 314 increases to lower the chargeability. Accordingly, the upperlimit for the ratio A/B is defined as 10/12 or less. Further, in a casewhere the A/B is less than 10/30 and the ratio of the binder resin 317increases excessively high, the sensitivity of the photoreceptor 310 islowered. Further, in a case of forming the charge transportation layer316 by a dip coating method to be described later, since the viscosityof the coating solution increases to lower the coating speed, theproductivity is worsened remarkably. Further, in a case of increasingthe amount of the solvent in the coating solution in order to suppressincrease of the viscosity of the coating solution, a brushing phenomenonoccurs to cause clouding in the formed charge transportation layer 316.Accordingly, the lower limit for the ratio A/B is defined as 10/30 ormore.

An additive such as a plasticizer or a leveling agent may also be addedto the charge transportation layer 316 optionally in order to improvethe film forming property, flexibility or surface smoothness. Theplasticizer include, for example, a dibasic acid ester such as phthalateester, fatty acid ester, phosphorate ester, chlorinated paraffin, andepoxy plasticizer. The leveling agent include, for example, siliconetype leveling agent.

Fine particles of an inorganic compound or an organic compound may beadded to the charge transportation layers 316 in order to increase themechanical strength or improve the electric characteristics.

Further, various additives such as an antioxidant or a sensitizer may beadded optionally to the charge transportation layer 316. This canimprove potential characteristics. Further, the stability of the coatingsolution upon forming the charge transportation layer 316 by coating canbe improved. Further, this can mitigate the fatigue deterioration toimprove the durability upon repetitive use of the photoreceptor.

As the antioxidant, hindered phenol derivatives or hindered aminederivatives are used preferably. The hindered phenol derivatives arepreferably used within a range of 0.1% by weight or more and 50% byweight or less relative to the charge transportation substance 313.Also, the hindered amine derivatives are used preferably within a rangefrom 0.1% by weight or more and 50% by weight or less relative to thecharge transportation substance 313. The hindered phenol derivative andthe hindered amine derivative may be used in admixture. In this case,the total amount of the hindered phenol derivative and the hinderedamine derivative to be used is preferably within a range from 0.1% byweight or more and 50% by weight or less relative to the chargetransportation substance 313. In a case where the amount of the hinderedphenol derivative to be used, the amount of the hindered aminederivative to be used, or the total amount of the hindered phenolderivative and the hindered amine derivative to be used is less than0.1% by weight, no sufficient effect can be obtained for the improvementof the stability of the coating solution and the improvement of thedurability of the photoreceptor. Further, if the amount exceeds 50% byweight, this gives an undesired effect on the characteristics of thephotoreceptor. Accordingly, it is defined as 0.1% by weight or more and50% by weight or less.

The charge transportation layer 316 is formed, for example, bydissolving or dispersing, in an appropriate solvent, the chargetransportation substance 313 containing the enamine compound representedby the general formula (2) described above and the binder resin 317 toprepare a coating solution for a charge transportation layer, andcoating the obtained coating solution on the outer circumferentialsurface of the charge generation layer 315.

As the solvent for the coating solution for charge transportation layer,those selected, for example, from the group consisting of aromatichydrocarbons such as benzene, toluene, xylene, and monochlorobenzene,halogenated hydrocarbons such as dichloromethane and dichloroethane,ether such as THF, dioxane, and dimethoxymethyl ether, as well asnon-protonic polar solvents such a N,N-dimethylformamide are used eachalone or in admixture of two or more of them. These solvents are usedeach alone or two or more of them in combination. Further, if necessary,a solvent such as alcohols, acetonitriles, or methyl ethyl ketone mayfurther be added to the solvent described above and used.

The coating method for the coating solution for charge transportationlayer includes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method or dip coating method.Among the coating methods described above, an optimal method can beselected while taking the physical properties of the coating and theproductivity into consideration. Among the coating methods describedabove, since the dip coating method is a method of dipping a substrateinto a coating bath filled with the coating solution and then pulling upthe substrate at a constant speed or at a gradually changing speed toform a layer on the surface of the substrate and, since the method isrelatively simple and excellent in view of the productivity and thecost, it has been often utilized in a case of producing anelectrophotographic photoreceptor and also often utilized in a case offorming the charge transportation layer 316.

The film thickness of the charge transportation layer 316 is preferably,5 μm or more and 50 μm or less and, more preferably, 10 μm or more and40 μm or less. In a case where the film thickness of the chargetransportation layer 316 is less than 5 μm, the charge retainability onthe surface of the photoreceptor is lowered. In a case where the filmthickness of the charge transportation layer 316 exceeds 50 μm,resolution of the photoreceptor is lowered. Accordingly, it is definedas 5 μm or more and 50 μm or less.

The charge generation layer 315 contains the charge generation substance312 as a main ingredient. The material effective as the chargegeneration substance 312 includes azo pigments such as a monoazopigment, bisazo pigment, and trisazo pigment, indigo pigments such asindigo and thioindigo, perylene pigments such as peryleneimide andperylenic acid anhydride, polynuclear quinone pigments such asanthraquinone and pyrenequinone, phthalocyanine pigments such as metalphthalocyanine and non-metal phthalocyanine, squarylium dyes, pyryliumsalts and thiopyrylium salts, triphenylmethane dyes, and inorganicmaterials such as selenium and amorphous silicon. The charge generationsubstances are used each alone or two or more of them in combination.

Among the charge generation substances described above, use ofoxotitanium phthalocyanine is preferred. Since oxotitaniumphthalocyanine is a charge generation substance having high chargegenerating efficiency and charge injecting efficiency, it generates agreat amount of charges by absorption of light and efficiently injectsthe generated charges, without accumulating them in the inside thereof,into the charge transportation substance 313. Further, for the chargetransportation substance 313, since the enamine compound of high chargemobility represented by the general formula (2) is used, the chargesgenerated from oxotitanium phthalocyanine as the charge generationsubstance 312 by light absorption are efficiently injected into theenamine compound represented by the general formula (2) as the chargetransportation substance 313 and transported smoothly to the surface ofthe photosensitive layer 314. Accordingly, by using oxotitaniumphthalocyanine as the charge generation substance 312 a photoreceptor310 of high sensitivity and high resolution can be obtained.

The charge generation substance 312 may be used in combination withsensitizing dyes, for example, triphenylmethane dyes typicallyrepresented by methyl violet, crystal violet, night blue, and Victoriablue, acrydine dyes typically represented by erythrosin, rhodamine B,rhodamine 3R, acrydine orange, and flaveosin, thiazine dyes typicallyrepresented by methylene blue andmethylene green, oxazine dyes typicallyrepresented by capri blue and merdora blue, cyanine dyes, stylyl dyes,pyrylium salt dyes, or thiopyrylium salt dyes.

The method of forming the charge generation layer 315 includes a methodof vapor depositing under vacuum the charge generation substance 312 onthe outer circumferential surface of the electroconductive substrate311, or a method of coating a coating solution for charge generationlayer obtained by dispersing the charge generation substance 312 in anappropriate solvent on the outer circumferential surface of theelectroconductive substrate 311. Among them, a preferred method includesdispersing the charge generation substance 312 into a binder resinsolution obtained by mixing a binder resin as a binder into anappropriate solvent by a known method to prepare a coating solution forcharge generation layer and coating the obtained coating solution on theouter circumferential surface of the electroconductive substrate 311.The method is to be described below.

The binder resin used for the charge generation layer 315 includes, forexample, polyester resin, polystyrene resin, polyurethane resin, phenolresin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylresin, methacryl resin, polycarbonate resin, polyarylate resin, phenoxyresin, polyvinyl butyral resin, and polyvinyl formal resin, as well ascopolymer resins containing two or more of repetitive units constitutingthe resins described above. Specific examples of the copolymer resininclude, for example, those insulative resins such as vinylchloride-vinyl acetate copolymer resin, vinyl chloride-vinylacetate-maleic acid anhydride copolymer resin, and acrylonitrile-styrenecopolymer resin. The binder resin is not restricted to them but thoseresins used generally can be used as the binder resin. The resins areused each alone or two or more of them in combination.

As a solvent for the coating liquid for charge generation layer, forexample, halogenated hydrocarbons such as dichloromethane ordichloroethane, ketones such as acetone, methyl ethyl ketone orcyclohexanone, esters such as ethyl acetate or butyl acetate, etherssuch as tetrahydrofuran (referred to as THF) or dioxane, alkylethers ofethylene glycol such as 1,2-dimethoxyethane, aromatic hydrocarbons suchas benzene, toluene or xylene, or aprotonic polar solvents such asN,N-dimethyl formamide or N,N-dimethylacetoamide, etc, are used. Thesolvents may be used alone or two or more of them may be mixed and usedas a mixed solvent.

As the blending ratio between the charge generation substance 312 andthe binder resin, it is preferred that the ratio of the chargegeneration substance 312 is within a range from 10% by weight to 99% byweight. In a case where the ratio of the charge generation substance 312is less than 10% by weight, the sensitivity of the photoreceptor 310 islowered. In a case where the ratio of the charge generation substance312 exceeds 99% by weight, since not only the film strength of thecharge generation layer 315 is lowered but also the dispersibility ofthe charge generation substance 312 is lowered to increase coarseparticles to sometimes decrease the surface charges at the portion otherthan the portion to be erased by exposure, this increases image defects,particularly, image fogging referred to as “black speck” where tonersare deposited to the white background to form fine black spots.Accordingly, it is defined as from 10% by weight to 99% by weight.

Before dispersing in the binder resin solution, the charge generationsubstance 312 may previously be pulverized by a pulverizer. Thepulverizer used for pulverization includes, for example, a ball mill,sand mill, attritor, vibration mill, and supersonic dispersing machine.

The dispersing machine used upon dispersing the charge generationsubstance 312 into the binder resin solution includes, for example, apaint shaker, ball mill, and sand mill. As the dispersion conditions,appropriate conditions are selected so as not to cause intrusion ofimpurities due to abrasion of members constituting the container ordispersing machine to be used.

The coating method of the coating solution for charge generation layerincludes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method, and dip coating method.Among the coating method described above, since the dip coating methodis particularly excellent with various view points as described above,it has been often utilized also in a case of forming the chargegeneration layer 315. As the apparatus used for the dip coating method,a coating solution dispersing apparatus typically represented by asupersonic wave generation apparatus may be provided in order tostabilize the dispersibility of the coating solution.

The film thickness of the charge generation layer 315 is, preferably,0.05 μm or more and 5 μm or less and, more preferably, 0.1 μm or moreand 1 μm or less. In a case where the film thickness of the chargegeneration layer 315 is less than 0.05 μm, the light absorptionefficiency is lowered to lower the sensitivity of the photoreceptor 310.In a case where the film thickness of the generation layer 315 exceeds 5μm, the charge transfer in the charge generation layer constitutes arate determining step in the process of erasing charges on the surfaceof the photoreceptor to lower the sensitivity of the photoreceptor 310.Accordingly, it is defined as 0.05 μm or more and 5 μm or less.

The photosensitive layer 314 has a stacked structure of the chargegeneration layer 315 and the charge transportation layer 316 formed asdescribed above. In this embodiment, while the photosensitive layer 314has a constitution in which the charge generation layer 315 and thecharge transportation layer 316 are stacked in this order on the outercircumferential surface of the electroconductive substrate 311, this isnot restrictive but it may be a constitution in which the chargetransportation layer 316 and the charge generation layer 315 are stackedin this order on the outer circumferential surface of theelectroconductive substrate 311. However, with a view point of thedurability, the photosensitive layer 314 preferably has a constitutionin which the charge generation layer 315 and the charge transportationlayer 316 are stacked in this order on the outer circumferential surfaceof the electroconductive substrate 311.

Further, the photosensitive layer 314 is not restricted to the stackedtype photosensitive layer having a stacked structure of the chargegeneration layer 315 and the charge transportation layer 316 but asingle-layered type photosensitive layer comprising the chargetransportation substance 313 containing the enamine compound representedby the general formula (2), the charge generation substance 312 and thebinder resin 317 are contained in a single layer may also be provided.However, it is more preferred to provide a stacked type photosensitivelayer having a stacked structure of the charge generation layer 315 andthe charge transportation layer 316. As described above, by sharing thecharge generating function and the charge transportation functionrespectively to separate layers, since materials optimal to the chargegenerating function and the charge transportation function can beselected for the materials constituting the respective layers, it ispossible to obtain a photoreceptor 310 of higher sensitivity having highreliability with further improved stability during repetitive usecompared with a case of providing the single layered type photosensitivelayer.

In a case of providing the single layered type photosensitive layer asthe photosensitive layer 314, the photosensitive layer is formed by thesame method as that for the charge transportation layer 316. Forexample, a single layered type photosensitive layer can be formed bydissolving or dispersing the charge generation substance 312, the chargetransportation substance 313 containing the enamine compound representedby the general formula (2), the binder resin 317 and, if necessary, theadditives described above into the same solvent as that of the coatingsolution for charge transportation layer to prepare a coating solutionfor photosensitive layer and by coating the coating solution forphotosensitive layer by way of a dip coating method, etc. on the outercircumferential surface of the electroconductive substrate 311.

Further, the ratio A′/B′ for the weight A′ of the enamine compoundrepresented by the general formula (2) and the weight B′ of the binderresin 317 in the single layered type photosensitive layer is preferablyfrom 10/12 to 10/30 in the same manner as the A/B for the weight A ofthe enamine compound represented by the general formula (2) and theweight B of the binder resin 317 in the charge transportation layer 316described above.

Further, one or more electron accepting materials or dyes may also beadded to the photosensitive layer 314 in order to improve thesensitivity and suppress the increase of the residual potential andfatigue during repetitive use.

As the electron accepting material, electron attracting materials, forexample, acid anhydrides such as succinic acid anhydride, maleic acidanhydride, phthalic acid anhydride, and 4-chloronaphthalic acidanhydride, cyano compound such as tetraethylcyanoethylene and terephthalmalon dinitrile, aldehydes such as 4-nitrobenzoaldehyde, anthraquinonessuch as anthraquinone and 1-nitroanthraquinone, polynuclear orheterocyclic nitro compounds such as 2,4,7-trinitrofluolenone and2,4,5,7-tetranitrofluolenone, as well as diphenoquinone compounds. Thoseformed by making the electron attracting materials to higher molecularweight, etc. may also be used.

As the dyes, organic photoconductive compounds, for example, xanthenedyes, thiazine dyes, triphenylmethane dyes, quinoline pigments, andcopper phthalocyanine can be used. Such organic photoconductivecompounds function as an optical sensitizer.

Further, various additives such as an antioxidant, a sensitizer, or aUV-absorber may be added optionally to each of the layers of thephotosensitive layer 314. This can improve potential characteristics.Further, the stability of the coating solution upon forming the layer bycoating can be improved. Further, this can mitigate the fatiguedeterioration to improve the durability upon repetitive use of thephotoreceptor.

Particularly preferred antioxidant includes, for example, phenolcompounds, hydroquinone compounds, to copherol compounds and aminecompounds. The antioxidant is preferably used within a range from 0.1%by weight or more and 50% by weight or less with respect to the chargetransportation substance 313. In a case where the amount of theantioxidant to be used is less than 0.1% by weight, no sufficient effectcan be obtained for the improvement of the stability of the coatingsolution and the durability of the photoreceptor. In a case where theamount of the antioxidant to be used exceeds 50% by weight, it gives anundesired effect on the characteristics of the photoreceptor.Accordingly, it is defined as 0.1% by weight or more and 50% by weightor less.

As the electroconductive material constituting the electroconductivesubstrate 311, for example, elemental metals such as aluminum, copper,zinc, and titanium, as well as alloys such as aluminum alloys andstainless steels can be used. Further, with no particular restriction tosuch metal materials, polymeric materials such as polyethyleneterephthalate, nylon, or polystyrene, hard paper or glass on which metalfoils are laminated, metal materials are vapor deposited, or a layer ofan electroconductive compound such as an electroconductive polymer, tinoxide, or indium oxide is vapor deposited or coated on the surfacethereof can also be used. These electroconductive materials are usedupon processing to a specified shape. While the shape of theelectroconductive substrate 311 is cylindrical in this embodiment, it isnot restrictive but various shapes may be adopted conforming the shapeof the photoreceptor 310.

The surface of the electroconductive substrate 311 may optionally beapplied with a surface treatment with chemicals or hot water, a coloringtreatment or a random reflection treatment, for example, by surfaceroughening, within a range not affecting the picture quality. In theelectrophotographic process using laser as an exposure source, since thewavelength of laser beams is coherent, the laser light reflected on thesurface of the photoreceptor and the laser light reflected in thephotoreceptor may sometimes cause interference and the interferencefringe caused by interference appears on the images to result in imagedefects. Image defects by the interference of the laser light ofcoherent wavelength can be prevented by applying the treatment describedabove to the surface of the electroconductive substrate 311.

The photoreceptor mounted to the image forming apparatus 301 of thisembodiment shown in FIG. 20 is not restricted to the photoreceptor 310having the layer constitution shown in FIG. 21 but photoreceptors havingvarious layer structures can be used. For example, a photoreceptor 410having the following layer constitution shown in FIG. 22 can be used.

FIG. 22 is a fragmentary cross sectional view schematically showinganother constitution of the photoreceptor mounted to the image formingapparatus 301 shown in FIG. 20. The photoreceptor mounted to the imageforming apparatus 301 of this embodiment may have a constitution inwhich an intermediate layer 318 is provided between theelectroconductive substrate 311 and the photosensitive layer 314 as inthe photoreceptor 410 shown in FIG. 22.

In a case where the intermediate layer 318 is not present between theelectroconductive substrate 311 and the photosensitive layer 314,charges are injected from the electroconductive substrate 311 to thephotosensitive layer 314 to lower the chargeability of thephotosensitive layer 314, and the surface charges in the portion otherthan the portions to be erased by exposure are decreased to sometimesresult in defects such as fogging to the images. Particularly, in a caseof forming images by using a reversal development process, since tonerimages are formed to the portion decreased with the surface charges byexposure, when the surface charges are decreased by the factor otherthan the exposure, fogging of images referred to as the black speck inwhich fine black spots are formed by the deposition of the toner on thewhite background to remarkably deteriorate the image qualities. That is,in a case where the intermediate layer 318 is not present between theelectroconductive substrate 311 and the photosensitive layer 314, thislowers the chargeability in the minute region due to the defects of theelectroconductive substrate 311 or the photosensitive layer 314 toresult in fogging of images such as black specks, which sometimes leadsto remarkable image defects.

In the photoreceptor 410 shown in FIG. 22, since the intermediate layer318 is provided between the electroconductive substrate 311 and thephotosensitive layer 314 as described above, injection of charges fromthe electroconductive substrate 311 to the photosensitive layer 314 canbe prevented. Accordingly, lowering of the chargeability in thephotosensitive layer 314 can be prevented to suppress the decrease ofthe surface charges in the portion other than the portion to be erasedby exposure, and occurrence of defects such as fogging in the images canbe prevented. Further, since provision of the intermediate layer 318 cancover the defects on the surface of the electroconductive substrate 311to obtain a uniform surface, the film forming property of thephotosensitive layer 314 can be improved.

For the intermediate layer 318, a resin layer

formed of various kinds of resin materials or an anodized film is used.Provision of the resin layer as the intermediate layer 318 can providealso an effect of suppressing the peeling of the photosensitive layer314 from the electroconductive substrate 311 to improve the adhesionbetween the electroconductive substrate 311 and the photosensitive layer314.

The resin materials forming the resin layer include, those resins suchas polyethylene resin, polypropylene resin, polystyrene resin, acrylresin, vinyl chloride resin, vinyl acetate resin, polyurethane resin,epoxy resin, polyester resin, melamine resin, silicone resin, polyvinylbutyral resin, and polyamide resin, as well as copolymer resinscontaining two or more of repetitive units constituting the resinsdescribed above. Further, casin, gelatin, polyvinyl alcohol, ethylcellulose, etc. can also be used. Among them, use of the polyamide resinis preferred and, particularly, use of alcohol soluble nylon resin ispreferred. Preferred alcohol soluble nylon resin includes, for example,so-called copolymerized nylon formed by copolymerizing 6-nylon,6,6-nylon, 6,10-nylon, 11-nylon and 2-nylon, as well as those resinformed by chemically modifying nylon such as N-alkoxymethyl modifiednylon and N-alkoxyethyl modified nylon.

In a case of providing a resin layer as the intermediate layer 318, itis preferred that the intermediate layer 318 is incorporated withparticles such as of metal oxide. Incorporation of the particles cancontrol the volumic resistance value of the intermediate layer 318 andimprove the effect of preventing injection of charges from theelectroconductive substrate 311 to the photosensitive layer 314, and canmaintain the electric characteristics of the photoreceptor under variouscircumstances.

The metal oxide particles include, for example, those particles oftitanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide.

The intermediate layer 318 comprising the resin layer is formed, forexample, by dissolving or dispersing the resin in an appropriate solventto prepare a coating solution for intermediate layer and coating thecoating solution on the outer circumferential surface of theelectroconductive substrate 311. In a case of incorporating particlessuch as of metal oxides to the intermediate layer 318, the intermediatelayer 318 can be formed, for example, by dissolving the resin describedabove into an appropriate solvent to obtain a resin solution, into whichthe particles are dispersed to prepare a coating solution forintermediate layer and coating the coating solution to the outercircumferential surface of the electroconductive substrate 311.

As the solvent for the coating solution of intermediate layer, water,various kinds of organic solvents or a mixed solvent thereof is used.Particularly, a single solvent such as water, methanol, ethanol, orbutanol, or mixed solvent such as water and alcohol, two or more kindsof alcohols, acetone or dioxolane and alcohols, and chlorine solventsuch as dichloroethane, chloroform, or trichloroethane and alcohols areused suitably.

As the method of dispersing the particles in the resin solution, ageneral method of using a ball mill, sand mill, attritor, vibrationmill, or supersonic dispersing machine, etc. can be used.

The total weight C for the resin and the metal oxide in the coatingsolution for intermediate layer relative to the weight D for the solventin the coating solution for intermediate layer is, preferably, from 1/99to 40/60 and, more preferably, from 2/98 to 30/70 as C/D. Further, theratio E/F between the weight E of the resin and the metal oxide is,preferably, from 90/10 to 1/99 and, more preferably, from 70/30 to 5/95.

The coating method of the coating solution for intermediate layerincludes, for example, a spraying method, a bar coating method, a rollcoating method, a blade method, wringing method, and a dip coatingmethod. Particularly, since the dip coating method is relatively simpleand is excellent in view of the productivity and the cost, it has beenoften utilized also in a case of forming the intermediate layer 318.

The film thickness of the resin layer provided as the intermediate layer318 is, preferably, from 0.01 μm or more and 20 μm or less and, morepreferably, 0.05 μm or more and 10 μm or less. In a case where the filmthickness of the resin layer is less than 0.01 μm, it no moresubstantially functions as the intermediate layer 318 and no uniformsurface property by coating the defects of the surface of theelectroconductive substrate 311 can be obtained, and injection ofcharges from the electroconductive substrate 311 to the photosensitivelayer 314 can not be prevented to lower the chargeability of thephotosensitive layer 314. It is not preferred to increase the filmthickness of the intermediate layer 318 to more than 20 μm sinceformation of the intermediate layer 318 is difficult and thephotosensitive layer 314 can not be formed uniformly on the outercircumferential surface of the intermediate layer 318 to lower thesensitivity of the photoreceptor in a case of forming the intermediatelayer 318 by the dip coating method.

In a case where the electroconductive substrate 311 comprises aluminum,an anodized film may also be provided instead of the resin layer as theintermediate layer 318. In a case of providing the resin layer as theintermediate layer 318, since there may be a possibility of causingdefects such as bruise to the intermediate layer 318, for example, byphysical impacts to generate leakage and cause image defects, a care hasto be taken in handling. However, since the anodized film is tough andless causes injuries, it is preferred to provide the anodized film asthe intermediate layer 318 with a view point of leakage proofness.

The anodized film can be formed by applying anodization to theelectroconductive substrate 311. The anodization is conducted in anacidic bath, for example, of chromic acid, sulfuric acid, oxalic acid,phosphoric acid, boric acid or sulfamic acid. Among them, theanodization in sulfuric acid provides a most preferred effect. In a caseof anodization in sulfuric acid, it is preferred to set the sulfuricacid concentration to 50 to 400 g/L, a dissolved aluminum concentrationto 2 to 20 g/L, the liquid temperature to 10 to 40° C., the electrolysisvoltage to from 5 to 30 V, and current density to 0.5 to 2 A/dm².

For improving the stability of the film, it is preferred that the thusformed anodized film is applied with a low temperature hole sealingtreatment of dipping into an aqueous solution containing nickel fluorideas a main ingredient, a high temperature hole sealing treatment ofdipping in an aqueous solution containing nickel acetate as a mainingredient, or other hole sealing treatment such as steam hole sealingor boiling water hole sealing and the like.

The average film thickness of the anodized film provided as theintermediate layer 318 is, preferably, 0.1 μm or more and 20 μm or lessand, more preferably, 1 μm or more and 10 μm or less. In a case wherethe average film thickness of the anodized film is less than 0.1 μm, itno more functions substantially as the intermediate layer 318 and cannot cover the defects on the surface of the electroconductive substrate311 to obtain uniform surface property, and injection of charges fromthe electroconductive substrate 311 to the photosensitive layer 314 cannot be prevented to lower the chargeability of the photosensitive layer314. In a case where the average film thickness of the anodized filmexceeds 20 μm, the sensitivity of the photoreceptor is lowered.Accordingly, it is defined as 0.1 μm or more and 20 μm or less.

Referring again to FIG. 20, the constitution and the operation of theimage forming apparatus 301 having the photoreceptor 310 is to bedescribed.

The image forming apparatus 301 is cylindrical and comprises aphotoreceptor 310 rotationally supported on a housing 388 and notillustrated driving means for rotationally driving the photoreceptor 310around a rotational axis 344 in the direction of an arrow 341. Thedriving means comprise, for example, a motor as a power source andtransmit the power from the motor by way of not illustrated gears to thesupport constituting the core of the photoreceptor 310 therebyrotationally driving the photoreceptor 310 at a predeterminedcircumferential speed. While the shape of the photoreceptor 310 iscylindrical in this embodiment, this is not limitative and may be acolumnar shape, an endless belt shape or the like.

At the periphery of the photoreceptor 310, are provided a contactcharger 332, image exposure means 330, a developing device 333, atransfer device 334, separation means 337, and a cleaner 336 in thisorder from the upstream to the downstream in the rotational direction ofthe photoreceptor 310 shown by the arrow 341. The cleaner 336 isprovided together with a not illustrated charge eliminator. Thephotoreceptor 310, the contact charger 332, the developing device 333and the cleaner 336 are provided integrally so as to be housed in thehousing 338 to constitute a process cartridge 320. The process cartridge320 is constituted attachable to and detachable from the image formingapparatus main body by using guide means such as not illustrated rails.

The contact charger 332 is contact charging means comprising a chargingmember 332 a and not illustrated pressure loading means for conductingcharging while contacting the charging member 332 a against the outercircumferential surface 343 of the photoreceptor 310. The chargingmember 332 a is pressed by the pressure loading means to the outercircumferential surface 343 of the photoreceptor 310 to form a contactportion. By the use of the contact charger 332 as the contact chargingmeans, an image forming apparatus 301 with less generation of ozonedeleterious to human bodies and usable for a long period of time can beattained.

The charging member 332 a is in a brush shape and constituted includingan electroconductive brush 350 and a cylindrical support 351 supportingthe electroconductive brush 350, and the support 351 is supportedrotationally, for example, on the housing 338. Since the charging member332 a have a brush-like shape, the contact portion between the chargingmember 332 a and the outer circumferential surface 343 of thephotoreceptor 310 is decreased to mitigate mechanical stress from thecharging member 332 a to the photosensitive layer 314 as the surfacelayer of the photoreceptor 310, the life of the photoreceptor 310 can beextended. Further, this can reduce the filming that occurs when thetoner remaining on the outer circumferential surface 343 of thephotoreceptor 310 is pressed to the surface 343 by the charging member332 a.

While the support 351 supporting the electroconductive brush 350 is acolumnar shape in this embodiment, this is not restrictive but may be acylindrical or plate-like shape. In a case where the shape of thesupport 351 is a columnar or cylindrical, the charging member 332 a isused while being driven rotationally by an external rotational drivingforce or the contact frictional force with the photoreceptor 310. In acase where the support 351 is in a plate-like shape, the charging member332 a is used being fixed.

The material constituting the charging member 332 a is not particularlylimited but it may be any material so long as desired electricalresistance and shape can be obtained. For example, metals such as goldor silver or electroconductive polymer can be used. Further, a resinmaterial in which an electroconductive powder such as of carbon black ormetal is dispersed, or a resin material applied with ionic conductiontreatment can also be used.

The charging member 332 a is connected with an external power source 339for applying a voltage. The outer circumferential surface 343 of thephotoreceptor 310 can be charged to a predetermined potential byapplying a voltage from the external power source 339 to the support 351in a state of abutting the electroconductive brush 350 of the chargingmember 332 a against the outer circumferential surface 343 of thephotoreceptor 310. As the voltage applied to the charging member 332 a,that is, to the support 351, only the DC voltage may be used but it ispreferred to use a vibrating voltage superposing an AC voltage to a DCvoltage in order to uniformly charge the outer circumferential surface343 of the photoreceptor 310.

The charging member 332 a is in a brush-shape in this embodiment but itis not restrictive and may also be a roller shape, a blade shape, a beltshape or a plate shape. With a view point for the stability of charging,it is preferred that the charging member 332 a is in a roller-likeshape. Since the contact portion between charging member 332 a and thephotoreceptor 310 increases when the charging member 332 a has aroller-like shape, the photoreceptor 310 can be charged stably.

In a case where the charging member 332 a is in a roller shape, thecharging member 332 a is constituted including a columnar or cylindricalsupport and an elastic layer covering the outer circumferential surfaceof the support. The elastic layer may be constituted with a singlelayer, or may be constituted with two layers of a support layer coveringthe outer circumferential surface of the support and a resistive layercovering the outer circumferential surface of the support layer.Further, a protective layer may also be disposed further to the outercircumferential surface of the elastic layer. The elastic layer, thesupport layer, the resistive layer and the protective layer are formedso as to have desired electric resistance. The outer circumferentialsurface 343 of the photoreceptor 310 can be charged to a predeterminedpotential by applying a voltage from the external power source 339 tothe support like in the case of the brush-like charging member 332 a, ina state of abutting the elastic layer, the resistive layer or protectivelayer to the outer circumferential surface 343 of the photoreceptor 310.

As the material constituting the support for the roller-shape chargingmember 332 a, electroconductive materials are used and, for example,metals such as gold or silver, or electroconductive polymers are used.Further, a resin material in which an electroconductive powder of carbonblack or metal is dispersed, or a resin material applied with ionicconduction treatment can also be used.

As the material constituting the elastic layer or the support layer,those having conductivity or semiconductivity are used and insulativeelastic materials to which electroconductive particles or semiconductiveparticles are dispersed are used suitably. The insulative elasticmaterial include, for example, rubber materials such as silicone rubber,polyurethane rubber, ethylene-propylene-diene copolymer (simply referredto as EPDM) rubber and nitrile rubber. The electroconductive particlesor semiconductive particles include, for example, carbon powder, carbonfiber, metal powder, and graphite.

As the material constituting the resistive layer or the protectivelayer, those having conductivity or semiconductivity are used, andbinder resins in which electroconductive particles or semiconductiveparticles are dispersed are used suitably. The binder resin include, forexample, acrylate resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxy methylated nylon, polyurethane resin,polycarbonate resin, polyethylene resin, polyvinyl resin such aspolyvinyl chloride, polyarylate resin, polythiophene resin, polyetserresin such as polyethylene terephthalate, polyolefin resin, fluorineresin, and styrene-butadiene copolymer resin. As the electroconductiveparticles or semiconductive particles, particles identical with thoseused for the elastic layer or support layer can be used.

The image exposure means 330 comprise, for example, a semiconductorlaser as the light source, and a light 331 such as a laser beamoutputted from the light source is irradiated to the outercircumferential surface 343 of the photoreceptor 310 situated betweenthe contact charger 332 and the developing device 333 in accordance withthe image information, to conduct image exposure to the charged outercircumferential surface 343 of the photoreceptor 310 to formelectrostatic latent images on the outer circumferential surface 343.

The developing device 333 is developing means for developingelectrostatic latent images formed by image exposure to the outercircumferential surface 343 of the photoreceptor 310 by a developer,which is disposed being opposed to the photoreceptor 310 and comprises adeveloping roller 333 a for supplying a toner to the outercircumferential surface 343 of the photoreceptor 310, and a casing 333 bthat rotationally supports the developing roller 333 a around arotational axis parallel with the rotational axis 344 of thephotoreceptor 310 and housing a developer containing the toner in theinner space thereof.

The transfer device 334 is transfer means for transferring toner imagesas visual images formed by development to the outer circumferentialsurface 343 of the photoreceptor 310 to transfer paper 345 as arecording medium supplied between the photoreceptor 310 and thetransferring device 334 by not illustrated conveying means in thedirection of an arrow 342 and it is disposed being opposed by way of theconveying means to the photoreceptor 310. In this embodiment, thetransfer device 334 is contact type transfer means having a transferroller 334 a, pressing the transfer roller 334 a to the photoreceptor310 on the side opposite to the contact surface of the transfer paper345 in contact with the outer circumferential surface 343 of thephotoreceptor 310 and applying a voltage from the external power supply340 to the transfer roller 334 a in a state of press contacting thephotoreceptor 310 and the transfer paper 345, thereby transferring thetoner images to the transfer paper 345. The transfer device 334 is notrestricted to such a contact type transfer means for conducting transferutilizing the pressing force but it may be non-contact type transfermeans for conducting transfer without using pressing-force. As thenon-contact type transfer means, those comprising, for example, a coronadischarger, and transferring toner images to the transfer paper 345 byapplying charges at a polarity opposite to that of the toner from thecorona discharger to the transfer paper 345 can be used.

Separation means 337 are means for separating the photoreceptor 310 andthe transfer paper 345 in press contact with each other.

A cleaner 336 is cleaning means for removing to recover the tonerremaining on the outer circumferential surface 343 of the photoreceptor310 after the transferring operation by the transfer device 334 and itcomprises a cleaning blade 336 a for peeling the toner remaining on theouter circumferential surface 343 of the photoreceptor 310 from theouter circumferential surface 343, and a recovery casing 336 b forcontaining the toner peeled by the cleaning blade 336 a.

Further, a fixing device 335 as fixing means for fixing the toner imagestransferred to the transfer paper 345 is disposed in the direction ofconveying the transfer paper 345 separated by the separation means 337from the photoreceptor 310. The fixing device 335 comprises a heatingroller 335 a having not illustrated heating means and a press roller 335b opposed to the heating roller 335 a and press contacted to the heatingroller 335 a to form a contact portion.

An image forming method according to a ninth embodiment of the inventionincludes a step of preparing an electrophotographic photoreceptor, acontact charging step of conducting charging while contacting a chargingmember to the obtained electrophotographic photoreceptor, an imageexposure step of conducting image exposure to the chargedelectrophotographic photoreceptor thereby forming electrostatic latentimages, and a developing step of developing the thus formedelectrostatic latent images, wherein the step of preparing theelectrophotographic photoreceptor includes preparing anelectroconductive substrate formed of an electroconductive material andforming a photosensitive layer containing an enamine compoundrepresented by the general formula (2) and a binder resin on theelectroconductive substrate. That is, the image forming method ispracticed by the image forming apparatus 301 according to thisembodiment.

An image forming operation by the image forming apparatus 301 is to bedescribed. At first, when the photoreceptor 310 is driven rotationallyby driving means in the direction of the arrow 341, the charging member332 a of the contact charger 332 located upstream to the focusing pointof the light 331 from the image exposure means 330 in the rotationaldirection of the photoreceptor 310 is pressed to the outercircumferential surface 343 of the photoreceptor 310 to form a contactportion. By applying a predetermined voltage from the external powersupply 339 to the charging member 332 a in this state, the outercircumferential surface 343 of the photoreceptor 310 is charged to apredetermined positive or negative potential.

Then, a light 331 is irradiated form the image exposure means 330 to theouter circumferential surface 343 of the photoreceptor 310 in accordancewith image information. The light 331 from the light source is scannedrepetitively in the longitudinal direction of the photoreceptor 310 as amain scanning direction. By rotationally driving the photoreceptor 310and repetitively scanning the light 331 from the light source, imageexposure is applied in accordance with the image information to theouter circumferential surface 343 of the photoreceptor 310. The imageexposure eliminates the surface charges at the portion irradiated withthe light 331 to cause a difference between the surface potential at theportion irradiated with the light 331 and the surface potential at theportion not irradiated with the light 331 to form electrostatic latentimages on the outer circumferential surface 343 of the photoreceptor310.

Then, when the toner is supplied to the outer circumferential surface343 of the photoreceptor 310 formed with electrostatic latent imagesfrom the developing the roller 333 a of the developing device 333located downstream to the focusing point of the light 331 from the lightsource in the rotational direction of the photoreceptor 310, theelectrostatic latent images are developed to form toner images to theouter circumferential surface 343 of the photoreceptor 310.

Further, in synchronization with image exposure to the photoreceptor310, transfer paper 345 is supplied by conveying means from thedirection of the arrow 342 to a position between the photoreceptor 310and the transfer device 334. When the transfer paper 345 is suppliedbetween the photoreceptor 310 and the transfer device 334, the transferroller 334 a of the transfer device 334 is pressed to the photoreceptor310 to form a contact portion, by which the photoreceptor 310 and thetransfer paper 345 are brought into press contact to each other. Byapplying a voltage from the external power supply 340 to the transferroller 334 a in this state, toner images formed on the outercircumferential 343 of the photoreceptor 310 is transferred to thetransfer paper 345.

The transfer paper 345 transferred with the toner images is separated bythe separation means 337 from the outer circumferential surface 343 ofthe photoreceptor 310, then conveyed by the conveying means to thefixing device 335 and heated and pressurized upon passage through thecontact portion between the heating roller 335 a and the press roller335 b of the fixing device 335. Thus, the toner images on the transferpaper 345 are fixed to the transfer paper 345 to form firm images. Thetransfer paper 345 thus formed with images is discharged by theconveying means to the outside of the image forming apparatus 301.

On the other hand, the toner remaining on the outer circumferentialsurface 343 of the photoreceptor 310 after the transferring operation bythe transfer device 334 is peeled by the cleaning blade 336 a of thecleaner 336 from the outer circumferential surface 343 of thephotoreceptor 310 and recovered in the recovering casing 336 b. Thecharges at the outer circumferential surface 343 of the photoreceptor310 thus removed with the toner are eliminated by a charge eliminatordisposed together with the cleaner 336, by which the electrostaticlatent images on the outer circumferential surface 343 of thephotoreceptor 310 are eliminated. Then, the photoreceptor 310 is furtherdriven rotationally to repeat a series of operations starting from thecharging to the photoreceptor 310 again. As described above, images areformed continuously.

When the charging is conducted in the image forming apparatus 301 bycontacting the charging member 332 a to the photoreceptor 310 by thecontact charger 332, a high electric field exerts concentrically to thecontact portion between the photosensitive layer 314 of thephotoreceptor 310 and the charging member 332 a. However, since thecharge transportation layer 316 as the surface layer of thephotosensitive layer 314 scarcely has defects as described above,charges supplied from the charging member 332 a are not concentrated toa portion in the charge transportation layer 316 and the photosensitivelayer 314 is uniformly charged. That is, the photosensitive layer 314does not suffer from dielectric breakdown by local leakage. Accordingly,it is possible to obtain an image forming apparatus 301 of highreliability capable of stably providing images at high quality with noimage defects caused leakage over a long period of time.

As an image forming apparatus 301 according to the eighth embodiment ofthe invention shown in FIG. 20, a test copying machine obtained bymodifying a charger of a commercially available copying machine(manufactured by Sharp Corp.: AR-265S) from a scorotron charger to acontact charger 332 having a brush-like charging member 332 a wasprovided and characteristics are evaluated. As the photoreceptor, 13types were prepared which were manufactured under the differentconditions respectively. The 13 kinds of the photoreceptors wereprepared respectively as described below.

Example 21

7 parts by weight of titanium oxide (manufactured by Ishihara SangyoCo.: TTO55A), and 13 parts by weight of copolymerized nylon resin(manufactured by Toray Co.: Amilan CM8000) were added to a mixed solventof 159 parts by weight of methanol and 106 parts by weight of1,3-dioxolane, and put to a dispersing treatment by a paint shaker for 8hours to prepare a coating solution for intermediate layer. The obtainedcoating solution for intermediate layer was filled in a coating tank,and a cylindrical aluminum electroconductive substrate 311 of 30 mmdiameter and 322.3 mm length size was dipped in and then pulling up fromthe coating tank and dried spontaneously to form an intermediate layer318 of 1 μm thickness.

Then, after adding one part by weight of oxotitanium phthalocyanine asthe charge generation substance 312 to a resin solution obtained bydissolving one part by weight of a polyvinyl butyral resin (manufacturedby Sekisui Chemical Industry Co.: S-LEC BX-1) in 98 parts by weight oftetrahydrofuran (THF), they were dispersed by a paint shaker for 2 hoursto prepare a coating solution for charge generation layer. After dipcoating the obtained coating solution for charge generation layer to theintermediate layer 318 formed previously in the same manner as thecoating solution for intermediate layer, it was dried spontaneously toform a charge generation layer 315 of 0.3 μm film thickness.

Then, 8 parts by weight of an enamine compound of Exemplified CompoundNo. 1 shown in Table 6 as the charge transportation substance 313, and10 parts by weight of a bisphenol Z polycarbonate resin (manufactured byMitsubishi Engineering Plastics Co.: Eupiron Z-200) are dissolved in amixed solvent of 40 parts by weight of tetrahydrofurn and 40 parts byweight of toluene to prepare a coating solution for chargetransportation layer. After dip coating the obtained coating solutionfor charge transportation layer on the previously formed chargegeneration layer 315 in the same manner as for the coating solution forintermediate layer described above, it was dried to form a chargetransportation layer 316 of 20 μm film thickness.

As described above, a stacked type electrophotographic photoreceptor ofthe layer constitution shown in FIG. 22 was prepared.

Examples 22 to 26

Five types of electrophotographic photoreceptors were prepared in thesame manner as in Example 21 except for using, instead of the enaminecompound of the Exemplified Compound No. 1, Exemplified Compound No. 3shown in Table 6, Exemplified Compound No. 61 shown in Table 14,Exemplified Compound No. 106 shown in Table 21, Exemplified Compound No.146 shown in Table 26, or the enamine compound of Exemplified CompoundNo. 177 shown in Table 31 for the charge transportation substance 313upon forming the charge transportation layer 316.

Example 27

An electrophotographic photoreceptor was prepared in the same manner asin Example 21 except for changing the amount of the enamine compound ofExemplified Compound No. 1 as the charge transportation substance 313 to5 parts by weight and changing the amount of the bisphenol Zpolycarbonate resin as the binder resin 317 to 13 parts by weight uponforming the charge transportation layer 316.

Example 28

An electrophotographic photoreceptor was prepared in the same manner asin Example 21 except for changing the amount of the enamine compound ofExemplified Compound No. 1 as the charge transportation substance 313 to4 parts by weight and the amount of the bisphenol Z polycarbonate resinas the binder resin 317 to 13 parts by weight upon forming chargetransportation layer 316.

Example 29

An electrophotographic photoreceptor was prepared in the same manner asin Example 21 except for changing the amount of the enamine compound ofExemplified Compound No. 1 as the charge transportation substance 313 to9 parts by weight and the amount of the bisphenol Z polycarbonate resinas the binder resin 317 to 9 parts by weight upon forming chargetransportation layer 316.

Example 30

An anodizing treatment was applied to a cylindrical aluminumelectroconductive substrate 311 identical with that in Example 21 and,after forming an anodizing film of 6 μm film thickness on theelectroconductive substrate 311, a hole sealing treatment was applied toform an intermediate layer 318. The anodizing treatment was conducted insulfuric acid under the conditions at a sulfuric concentration of 180g/L, a dissolved aluminum concentration of 4.5 g/L, a liquid temperatureof 20° C., an electrolysis voltage of 10 V, and a current density of 1.5A/dm².

Then, in the same manner as in Example 21, a charge generation layer 315and a charge transportation layer 316 were formed, to prepare anelectrophotographic photoreceptor.

Comparative Example 13

An electrophotographic photoreceptor was prepared in the same manner asin Example 21 except for using a comparative compound represented by thefollowing structural formula (28) instead of the enamine compound ofExemplified Compound No. 1 as the charge transportation substance 313.In the followings, the comparative compound represented by the followingstructural formula (28) is sometimes referred to as TPD.

[Ka 44]

Comparative Example 14

An electrophotographic photoreceptor was prepared in the same manner asin Example 21 except for using 5 parts by weight of the ComparativeCompound (TPD) represented by the structural formula (28) instead of 8parts by weight of the enamine compound of Exemplified Compound No. 1 asthe charge transportation substance 313 and changing the amount of thebisphenol Z polycarbonate resin as the binder resin 317 to 13 parts byweight.

Comparative Example 15

An electrophotographic photoreceptor was prepared in the same manner asin Example 21 except for using a comparative compound represented by thefollowing structural formula (29) instead of the enamine compound ofExemplified Compound No. 1 as the charge transportation substance 313.In the followings, the comparative compound represented by the followingstructural formula (29) is sometimes referred to as ENA.

[Ka 45]

<Evaluation for Physical Property>

Physical properties were evaluated as described below.

The half-tone images were formed on transfer paper by using a testcopying machine to which photoreceptors prepared in Examples 21 to 30and Comparative Examples 13 to 15 were mounted respectively. The halftone images are images expressing the image density by gradation inblack and white dots. For the obtained half-tone images, image densitywas measured as the reflectance density by using a Macbeth densitometer(manufactured by Macbeth Co.: RD914), which was compared with apredetermined allowable range for the image density. Further, obtainedhalf-tone images were observed with naked eyes to confirm the presenceor absence of black spots and white spots. Based on the results, theimage quality of the obtained half-tone images was evaluated.

The evaluation criterion for the image quality is as described below.

-   ◯: good. The image density is substantially equal with the central    value in the allowable range as a standard. Neither black spots nor    white spots are present.-   Δ: no practical problem. While the image density is lower or    somewhat lower than the central value within the allowable range as    the standard, it is within the allowable range. Neither black spots    nor white spots are present.-   x: not endurable for actual use. The image density is low being out    of the allowable range, or black spots or white spots are formed.

Then, the developing device was taken out of the test copying machineand, instead, a surface potential meter was attached to the developingportion (manufactured by Trek Co.: Model 1344) to measure a surfacepotential V0 (−V) of the photoreceptor when a solid white original wascopied, a surface potential VH (−V) of the photoreceptor when ahalf-tone original was copied, and a surface potential VL (−V) of thephotoreceptor when a solid black original was copied thereby evaluatingelectric characteristics. In this test copying machine, reversaldeveloping process was adopted.

The result of the evaluation described above was the result ofevaluation for the initial stage.

Then, the surface potential meter was taken out and the developingmachine was mounted again. After copying images of a predeterminedpattern by 30,000 sheets of A4 size copy paper according to JapaneseIndustrial Standards (JIS) P0138, half-tone images were further formed.For the obtained half-tone images, quality of the images was evaluatedin the same manner as in the initial stage. The standard criterion wasidentical with that in the initial stage. Further, the surfacepotentials V0, VH, and VL of the photoreceptor were measured in the samemanner as that in the initial stage. The result of the evaluationdescribed above was the result of the evaluation after repetitive use.

The result of evaluation is shown in Table 45.

TABLE 45 Charge transportation layer Charge Charge transportationInitial stage After repetitive use transportation substance/Intermediate V0 VH VL V0 VH VL substance binder resin layer (−V) (−V)(−V) Image quality (−V) (−V) (−V) Image quality Example 21 Exemplified10/12.5 Resin layer 600 350 75 ◯ 590 360 85 ◯ Compound 1 Example 22Exemplified 10/12.5 Resin layer 600 360 85 ◯ 590 375 95 ◯ Compound 3Example 23 Exemplified 10/12.5 Resin layer 600 350 75 ◯ 590 360 85 ◯Compound 61 Example 24 Exemplified 10/12.5 Resin layer 600 350 75 ◯ 590360 85 ◯ Compound 106 Example 25 Exemplified 10/12.5 Resin layer 600 36085 ◯ 590 370 95 ◯ Compound 146 Example 26 Exemplified 10/12.5 Resinlayer 600 365 90 ◯ 590 375 95 ◯ Compound 177 Example 27 Exemplified10/26   Resin layer 600 395 100 ◯ 600 395 105 Δ Compound 1 (imagedensity somewhat low) Example 28 Exemplified 10/32.5 Resin layer 600 400105 Δ 600 455 155 Δ Compound 1 (image density, (image somewhat low)density low) Example 29 Exemplified 10/10   Resin layer 600 350 75 ◯ 590390 110 Δ Compound 1 (image density somewhat low) Example 30 Exemplified10/12.5 Anodized film 600 355 80 ◯ 590 365 90 ◯ Compound 1 Comp. Ex. 13TPD 10/12.5 Resin layer 600 420 130 Δ 585 480 180 X (image (black spotsdensity low) formed) Comp. Ex. 14 TPD 10/26   Resin layer 600 450 150 Δ595 500 200 X (image (image density, density low) out or the range)Comp. Ex. 15 ENA 10/12.5 Resin layer 600 360 85 ◯ 590 450 150 Δ (imagedensity low)

From the comparison between Examples 21 to 26 and Comparative Example13, it was found that each photoreceptor of Examples 21 to 26 using theenamine compound represented by the general formula (2) for the chargetransportation substance had a smaller absolute value VL both in theinitial stage and after the repetitive use and was excellent in thesensitivity and the responsivity, compared with the photoreceptor ofComparative Example 13 using TPD. Further, it was found that eachphotoreceptor of Examples 21 to 26 had a smaller difference between thevalues for VO, VH, and VL in the initial stage and the values for VO,VH, and VL after the repetitive use and was excellent in the electricdurability, compared with the photoreceptor of Comparative Example 13.

Further, it was found that the copying machine on which thephotoreceptors of Examples 21 to 26 were mounted could provide images ofgood quality both in the initial stage and after the repetitive use. Onthe other hand, the copying machine on which the photoreceptor ofComparative Example 13 was mounted, injuries of the photosensitive layercaused by leakage appeared as black spots on the image after therepetitive use. It is considered to be attributable to that TPD used inthe photoreceptor of Comparative Example 13 is inferior in thecompatibility with the binder resin and the solubility to the solvent,compared with the enamine compound represented by the general formula(2) used for each photoreceptor of Examples 21 to 26.

That is, since the enamine compound represented by the general formula(2) was excellent in the compatibility with the binder resin and thesolubility to the solvent, agglomeration of the enamine compound did notoccur and a uniform photosensitive layer was formed in eachphotoreceptor of Examples 21 to 26 to which this enamin compound wasused. Accordingly, for the copying machine on which each photoreceptorof Examples 21 to 26 was mounted, it is considered that charges were notconcentrated to a portion in the photosensitive layer and good imagequality could be kept also after the repetitive use even when chargingwas conducted by a contact charger exerting high electric fieldconcentrically to the contact portion between the photoreceptor and thecharging member. On the other hand, since TPD used for the photoreceptorof Comparative Example 13 was poor in the compatibility with the binderresin and the solubility to the solvent, the photosensitive layer in thephotoreceptor of Comparative Example 13 was uniform in view of visualobservation but an agglomerated portion of TPD was actually formed.Accordingly, it is considered that the charges were concentrated to theportion where TPD was agglomerated when charging was conducted by thecontact charger, the photosensitive layer suffered from insulationbreakdown and as a result, black spot appeared on the images.

Further, it was found from Comparative Example 14 that even in a case ofusing TPD for the charge transportation substance, black spots caused byleakage could be overcome by defining the ratio between the weight ofTPD as the charge transportation substance and the weight of the binderresin (charge transportation substance/binder resin) to 10/26, that is,by decreasing the ratio of TPD and increasing the ratio of the binderresin than the photoreceptor of Comparative Example 13. This isconsidered to be attributable to that TPD was uniformly dissolved in thecoating solution since the TPD ratio was lower to form thephotosensitive layer as a uniform coating film. However, in the copyingmachine on which the photoreceptor of Comparative Example 14 wasmounted, the sensitivity of the photoreceptor was insufficient and theimage density was decreased to less than the standard, and images formedafter the repetitive use were not suitable for actual use.

On the contrary, in the photoreceptor of Example 27, while the ratio A/Bfor the weight A of the enamine compound represented by the generalformula (2) which is the charge transportation substance and the weightB of the binder resin was defined as 10/26 like in Comparative Example14, that is, the ratio of the enamine compound was lowered and the ratioof the binder resin was increased than that of the photoreceptor ofExample 21, but the sensitivity was sufficient and images of qualitywith no practical problem could be obtained even after the repetitiveuse in the copying machine on which the photoreceptor of Example 27 wasmounted. This is considered to be attributable to that the chargemobility of the enamine compound represented by the general formula (2)is high.

Further, from the comparison between Example 21 and Example 28, it wasfound that the photoreceptor of Example 28 in which the ratio of thebinder resin was further increased than that in the photoreceptor ofExample 27 with the ratio A/B being defined as less than 10/30, thecharge transportation ability of the photoreceptor was lowered, theabsolute value of VL was increased and the sensitivity and theresponsivity were lowered compared with the photoreceptor of Example 21.Further, for the copying machine on which the photoreceptor of Example28 was mounted, it was found that while the images obtained in theinitial stage was somewhat lower than the standard, images obtainedafter repetitive use were further lowered in the image density by theaccumulation of residual potential.

Further, from the comparison between Example 21 and Example 29, in acopying machine mounting the photoreceptor of Example 29 in which theratio A/B exceeded 10/12, the ratio of the enamine compound representedby the general formula (2) is increased and the ratio of the binderresin was lowered than in the photoreceptor of Example 21, while imagesof good quality in the initial stage like in the copying machinemounting the photoreceptor of Example 21, a phenomenon that the imagedensity decreased somewhat was observed after the repetitive use. Thisis considered to be attributable to that the photoreceptor of Example 29had good electric characteristics identical with that of thephotoreceptor of Example 21 in the initial stage, but the chargeabilityof the photosensitive layer was lowered after the repetitive use sincethe wear amount of the photosensitive layer due to repetitive use waslarger compared with that of the photoreceptor of Example 21. That is,in the case of charging by using the contact charger, since the chargerand the photoreceptor are in contact with each other, charges move fromthe charger to the surface of the photoreceptor until the surfacepotential of the photoreceptor is equal with the potential of thecharger. When the chargeability of the photoreceptor is lowered, theamount of charges moving from the charger to the surface of thephotoreceptor increases till the potential becomes identical with thatof the charger by so much as the lowering of the chargeability. Asdescribed above, since the amount of surface charges in the imageexposure portion of the photoreceptor of Example 29 increases, morecharges remain on the surface of the photoreceptor at the image exposurewith the same amount of exposure as that for the photoreceptor ofExample 21. Accordingly, in the photoreceptor of Example 29, theabsolute value for VH and the absolute value for VL were increased morecompared with the photoreceptor of Example 21, the amount of the tonerdeposited to the surface of the photoreceptor at a portion where thecharges were decreased was decreased upon development and the imagedensity was somewhat lowered as described above. Further also the imagesformed after the repetitive use showed no problem in view of actual use.

Further, from the comparison between Example 21 and Example 30, it wasfound that the photoreceptor of Example 30 in which an anodized film wasdisposed as an intermediate layer had good electric characteristics bothin the initial stage and after the repetitive use like the photoreceptorof Example 21 in which a resin layer was disposed as an intermediatelayer. Further, for the copying machine where the photoreceptor ofExample 30 was mounted, it was found that good images were obtained andimage defects caused by leakage did not occur even after the repetitiveuse like the copying machine on which the photoreceptor of Example 21was mounted.

Further, from the comparison between Examples 21 to 26 and ComparativeExample 15, it was found each the photoreceptor of Examples 21 to 26using the enamine compound represented by the general formula (2) forthe charge transportation substance had a smaller difference between thevalues for VH and VL in the initial stage and the values for VH and VLafter the repetitive use, and was excellent in the electricaldurability, compared with the photoreceptor of Comparative Example 15using ENA as the enamine compound represented by the structural formula(29) not included in the general formula (2).

As described above, it was found that the copying machine mounting thephotoreceptor containing the enamine compound represented by the generalformula (2) in the photosensitive layer could obtain images at highquality with no image defects caused by leakage even when charging wasconducted while contacting the charging member to the photoreceptor.

The present invention, can be practice in various other embodimentswithout departing the spirit or the principal feature thereof.Accordingly, the embodiments described previously are merely examples inevery respect and the range of the invention is shown in the scope ofthe claims for patent and is no way restricted to the description of thespecification. Further, all modifications or changes belonging to thescope of the claims are within the range of the invention.

INDUSTRIAL APPLICABILITY

As has been described above, according to the present invention, sincethe photosensitive layer disposed on the electroconductive substrate ofthe electrophotographic photoreceptor contains a polyarylate resinhaving the specified structural unit of excellent mechanical strengthand an enamine compound having the the specified structure excellent inthe compatibility with the polyarylate resin having the specifiedstructural unit and having high charge mobility, it is possible toprovide an electrophotographic photoreceptor excellent in the mechanicalstrength, capable of enduring the increase of mechanical strengthaccompanied to digitalization and increasing resolution of theelectrophotographic apparatus, as well as having high durability capableof providing satisfactory electric characteristics stably over a longperiod of time.

Further, according to the invention, since the photosensitive layercontains the polyarylate resin having the structural unit of thecharacteristics excellent in the solubility to the solvent, thestability of the coating solution can be improved to improve theproduction efficiency of the electrophotographic photoreceptor in a caseof forming the photosensitive layer by coating.

Further, according to the invention, since the photosensitive layercontains the enamine compound of the specified structure having aparticularly high charge mobility, it is possible to attain anelectrophotographic photoreceptor having high charge potential, highsensitivity, exhibiting sufficient responsivity, excellent in durabilityand of high reliability with no deterioration of the characteristicseven in a case of use in a high speed electrophotographic process.

Further, according to the invention, since the photosensitive layer hasa stacked structure in which a charge generation layer containing acharge generation substance, and a charge transportation layercontaining a charge transportation substance containing an enaminecompound of a specified structure of high charge mobility and a chargetransportation layer containing a polyarylate resin having a specifiedstructural unit excellent in the mechanical strength are stacked in thisorder from the electroconductive substrate to the outside, it ispossible to provide an electrophotographic photoreceptor of highersensitivity, high durability, excellent in wear resistance and with lesschange of characteristics due to film scraping of the photosensitivelayer.

Further, according to the invention, since the intermediate layer isprovided between the electroconductive substrate and the photosensitivelayer, it is possible to prevent lowering of the chargeability of thephotosensitive layer and prevent occurrence of defects such as foggingto images, as well as improve the film forming property of thephotosensitive layer and adhesion between the electroconductivesubstrate and the photosensitive layer.

Further, according to the invention, since the process cartridgeattachable to and detachable from the electrophotographic apparatus mainbody integrally comprises an electrophotographic photoreceptor excellentin the mechanical strength, capable of enduring the increase of themechanical strength accompanied to digitalization and increasingresolution of the electrophotographic apparatus and capable of providingsatisfactory electric characteristics stably for a long period of timeand at least one of means selected from the group consisting of chargingmeans, developing means and cleaning means, it is possible to provide aprocess cartridge capable of easily attaching or detaching theelectrophotographic photoreceptor, and at least one of means selectedfrom the group consisting of charging means, developing means andcleaning means to and from the electrophotographic apparatus main bodyand not requiring exchange for a long period of time.

Further, according to the invention, since the electrophotographicphotoreceptor provided to the electrophotographic apparatus is excellentin the mechanical strength, capable of enduring increase of themechanical stress accompanied to the digitalization and increasingresolution of the electrophotographic apparatus and capable of providingsatisfactory electric characteristics stably for a long period of time,it is possible to provide an electrophotographic apparatus of highreliability capable of providing images at high quality for a longperiod of time.

Further, according to the invention, since the transfer means providedto the electrophotographic apparatus transfer developed images to arecording medium by press contacting the electrophotographicphotoreceptor and the recording medium, and the photosensitive layer ofthe electrophotographic photoreceptor contains the polyarylate resinhaving the specified structural unit of excellent mechanical strength,it is possible to attain an electrophotographic apparatus of highreliability capable of increasing the pressing force by the transfermeans, improving the transferring efficiency to the recording medium andcapable of providing images at high quality with less transfer deviationor image defects such as whitening or blanking.

Further, according to the invention, since the photosensitive layerprovided on the electroconductive substrate of the electrophotographicphotoreceptor is excellent in the mechanical strength and contains thepolycarbonate resin having the asymmetric diol ingredient exhibitinghigh solubility to a solvent whether the solvent is a halogen typeorganic solvent or non-halogen type organic solvent and the enaminecompound of high charge mobility having the specified structure, it ispossible to provide an electrophotographic photoreceptor having highcharge potential and charge retainability, high sensitivity and havingsufficient light responsivity, as well as is excellent in the durabilitynot deteriorating the characteristics even in a case of use under a lowtemperature circumstance or in a high speed electrophotographic process,having high reliability, and satisfactory productivity.

Further, according to the invention, since the photosensitive layercontains the enamine compound of a specific structure that has aparticularly high charge mobility, can be synthesized relatively easilyat a high yield and can be produced at a reduced cost, anelectrophotographic photoreceptor showing a further higher lightresponsivity can be produced at a reduced manufacturing cost.

Further, according to the invention, since the photosensitive layercontains a polycarbonate resin of particularly high mechanical strengthhaving a structural unit containing a specified asymmetric diolingredient, it is possible to obtain an electrophotographicphotoreceptor particularly excellent in the durability, with lessoccurrence of injuries at the surface of the photosensitive layer andwith less film reduction amount for the photosensitive layer.

Further, according to the invention, since the photosensitive layercontains a polycarbonate resin having an asymmetric diol ingredient anda siloxane structure, the surface friction coefficient of thephotosensitive layer is decreased to improve the slidability and thetransfer efficiency or the cleaning performance can be improved toobtain good images, injuries less occur to the surface of thephotosensitive layer, and abnormal sounds referred to as ringing areless generated.

Further according to the invention, since the photosensitive layerfurther contains oxotitanium phthalocyanine having high chargegeneration efficiency and charge injection efficiency, having an maximumabsorption peak in a wavelength region of a laser light irradiated froman infrared laser, an electrophotographic photoreceptor of highsensitivity and high resolution can be obtained and high quality imagescan be provided in a digital image forming apparatus using the infraredlaser as an exposure light source.

Further, according to the invention, since the photosensitive layer hasthe stacked structure at least of the charge generation layer containingthe charge generation substance and the charge transportation layercontaining the charge transportation substance containing the enaminecompound of high charge mobility having a specified structure, and atleast the charge transportation layer of the charge generation layer andthe charge transportation layer contains the polycarbonate resin havingthe asymmetric diol ingredient, it is possible to obtain anelectrophotographic photoreceptor of higher sensitivity and with highdurability with increased stability during repetitive use, and theproductivity of the electrophotographic photoreceptor can be improved.

Further, according to the invention, since the binder resin containingthe polycarbonate resin having the asymmetric diol ingredient can beincorporated at a high concentration in the charge transportation layerwithout deteriorating the light responsivity, it is possible to improvethe printing resistance of the charge transportation layer, suppress thechange of characteristics caused by the wear of the photosensitive layerthereby capable of improving the durability of the electrophotographicphotoreceptor.

Further according to the invention, since the electrophotographicphotoreceptor provided to image forming apparatus has high chargepotential and charge retainability, high sensitivity and sufficientlight responsivity, and also excellent in the durability with nodeterioration of the characteristics even in a case of use under a lowtemperature circumstance or in a high speed electrophotographic process,or exposure to light, it is possible to obtain an image formingapparatus of high reliability capable of providing images at a highquality for a long period of time under various circumstances, andlowering of the image quality due to exposure of the electrophotographicphotoreceptor to light, for example, during maintenance can be preventedto improve the reliability of the image forming apparatus.

1. An electrophotographic photoreceptor comprising: an electroconductivesubstrate formed of an electroconductive material; and a photosensitivelayer disposed on the electroconductive substrate and containing apolyarylate resin having a structural unit represented by the followinggeneral formula (1) and an enamine compound represented by the followinggeneral formula (2):

in which X¹ represents a single bond or —CR⁵R⁶—; R⁵ and R⁶ eachrepresents a hydrogen atom, a halogen atom, an alkyl group which mayhave a substituent, or an aryl group which may have a substituent;further, R⁵ and R⁶ may join to each other to form a ring structure; R¹,R², R³, and R⁴ each represents a hydrogen atom, a halogen atom, an alkylgroup which may have a substituent or an aryl group which may have asubstituent; and wherein R⁷˜R¹⁰ means R⁷, R⁸, R⁹, and R¹⁰ and whereinR⁷, R⁸, R⁹, and R¹⁰ each is directly attached to a different carbon atomon the indicated benzene ring not occupied by an ester group, and eachrepresents a hydrogen atom, a halogen atom, or an alkyl group which mayhave a substituent or an aryl group which may have a substituent

in which Ar¹ and Ar² each represents an aryl group selected from phenyl,naphthyl, pyrenyl, and anthryl groups which may have a substituent or aheterocyclic group selected from furyl, thienyl, thiazolyl, benzofuryl,benzothiophenyl, benzothiazolyl, and benxoxazolyl groups which may havea substituent; Ar³ represents an aryl group which may have asubstituent, a heterocyclic group which may have a substituent, anaralkyl group which may have a substituent, or an alkyl group which mayhave a substituent; Ar ⁴ and Ar⁵ each represents a hydrogen atom, anaryl group which may have a substituent, a heterocyclic group which mayhave a substituent, an aralkyl group which may have a substituent, or analkyl group which may have a substituent; however, both Ar⁴ and Ar⁵ donot form the hydrogen atoms; Ar⁴ and Ar⁵ may join to each other by wayof an atom or an atomic group to form a ring structure; “a” representsan alkyl group which may have a substituent, an alkoxy group which mayhave a substituent, a dialkylamino group which may have a substituent,an aryl group which may have a substituent, a halogen atom or a hydrogenatom, and m represents an integer of 1 to 6; in a case where m is 2 ormore, plural a may be identical or different with each other or may jointo each other to form a ring structure; R¹¹ represents a hydrogen atom,a halogen atom, or an alkyl group which may have a substituent; R¹²,R¹³, and R¹⁴ each represents a hydrogen atom, an alkyl group which mayhave a substituent, an aryl group which may have a substituent, aheterocyclic group which may have a substituent, or an aralkyl groupwhich may have a substituent; n represents an integer of 1 to 3 and in acase where n is 2 or 3, plural R¹² may be identical or different witheach other, and plural R¹³ may be identical or different with eachother; the substituent which may be present on Ar¹, Ar², Ar⁴, Ar⁵, a,R¹², R¹³, and R¹⁴ is selected from an alkyl group, an alkenyl group, analkoxy group, an amino group, a halogen group, an aryl group, an aryloxygroup, and an arylthio group; the substituent which may be present onAr³ is selected from an alkyl group, an alkoxy group, an amino group, ahalogen group, an aryl group, an aryloxy group, and an arylthio group.2. The electrophotographic photoreceptor of claim 1, wherein thephotosensitive layer contains a polyarylate resin having a structuralunit represented by the general formula (1), in which X¹ is —CR⁵R⁶—,each of R¹, R², R³, R⁴ R⁵ and R⁶ is a methyl group and each of R⁷, R⁸,R⁹, and R¹⁰ is a hydrogen atom.
 3. The electrophotographic photoreceptorof claim 1, wherein the enamine compound represented by the followingformula (2) is an enamine compound represented by the following generalformula (3);

wherein b, c and d each represent an optionally-substituted alkyl group,an optionally-substituted alkoxy group, an optionally-substituteddialkylamino group, an optionally-substituted aryl group, a halogenatom, or a hydrogen atom; i, k and j each indicate an integer of from 1to 5; and when i is 2 or more, then the “b”s may be the same ordifferent and may bond to each other to form a cyclic structure; when kis 2 or more, then the “c”s may be the same or different and may bond toeach other to form a cyclic structure; and when j is 2 or more, then the“d”s may be the same or different and may bond to each other to form acyclic structure; Ar⁴, Ar⁵, “a” and “m” represent the same as thosedefined in formula (1).
 4. The electrophotographic photoreceptor ofclaim 1, wherein the photosensitive layer has a stacked structure inwhich a charge generation layer containing a charge generation substanceand a charge transportation layer containing the charge transportationsubstance containing the enamine compound represented by the generalformula (2) and a polyarylate resin having the structural unitrepresented by the general formula (1) are stacked in this order to theoutside from the electroconductive substrate.
 5. The electrophotographicphotoreceptor of claim 1, wherein an intermediate layer is disposedbetween the electroconductive substrate and the photosensitive layer. 6.A process cartridge attachable to and detachable from anelectrophotographic apparatus main body, integrally comprising: theelectrophotographic photoreceptor of claim 1; and at least one of meansselected from the group consisting of charging means for charging theelectrophotographic photoreceptor, developing means for developingelectrostatic latent images formed by subjecting the electrophotographicphotoreceptor to exposure to light, and cleaning means for cleaning theelectrophotographic photoreceptor after transferring the developedimages onto a recording medium.
 7. An electrophotographic apparatuscomprising: the electrophotographic photoreceptor of claim 1; chargingmeans for charging the electrophotographic photoreceptor; exposure meansfor subjecting the charged electrophotographic photoreceptor to exposureto light; developing means for developing electrostatic latent imagesformed by the exposure to light; and transfer means for transferring thedeveloped images onto a recording medium.
 8. The electrophotographicapparatus of claim 7, wherein the transfer means transfer developedimages onto the recording medium by press contacting theelectrophotographic photoreceptor and the recoding medium.
 9. Theelectophotographic apparatus of claim 1, wherein the photosensitivelayer includes a charge generation substance including any combinationof a monoazo pigment, bisazo pigment, trisazo pigment, indigo,thioindigo, peryleneimide, perylenic acid anhydride, anthraquinone,pyrenequinone, metal phthalocyanine, non-metal phthalocyanine,squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethanedyes, selenium, and amorphous silicon.